WO2013094404A1 - 二次電池用活物質、二次電池および電子機器 - Google Patents
二次電池用活物質、二次電池および電子機器 Download PDFInfo
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- WO2013094404A1 WO2013094404A1 PCT/JP2012/081479 JP2012081479W WO2013094404A1 WO 2013094404 A1 WO2013094404 A1 WO 2013094404A1 JP 2012081479 W JP2012081479 W JP 2012081479W WO 2013094404 A1 WO2013094404 A1 WO 2013094404A1
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- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
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- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/386—Silicon or alloys based on silicon
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- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
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- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
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- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
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- H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
- H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/523—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron for non-aqueous cells
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- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
- H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
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- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
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- H01M4/66—Selection of materials
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- H01M4/663—Selection of materials containing carbon or carbonaceous materials as conductive part, e.g. graphite, carbon fibres
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- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
Definitions
- the present technology relates to an active material for a secondary battery capable of inserting and extracting lithium ions, a secondary battery using the active material for the secondary battery, and an electronic device using the secondary battery.
- the secondary battery is not limited to the above-described electronic device, but is a battery pack that is a detachable power source, an electric vehicle such as an electric vehicle, an electric power storage system such as a household electric power server, or an electric tool such as an electric drill.
- the secondary battery includes an electrolyte solution together with a positive electrode and a negative electrode, and the negative electrode includes a negative electrode active material capable of occluding and releasing lithium ions and the like.
- a carbon material such as graphite is widely used, but recently, since further improvement in battery capacity is required, the use of Si has been studied. This is because the theoretical capacity of Si (4199 mAh / g) is much larger than the theoretical capacity of graphite (372 mAh / g), so that significant improvement in battery capacity can be expected.
- the negative electrode active material expands and contracts violently during charge and discharge, so that the negative electrode active material tends to break mainly near the surface layer.
- the negative electrode active material is cracked, a highly reactive new surface (active surface) is generated, and the surface area (reaction area) of the negative electrode active material is increased.
- a decomposition reaction of the electrolytic solution occurs on the new surface, and the electrolytic solution is consumed to form a coating film derived from the electrolytic solution on the new surface, so that battery characteristics such as cycle characteristics are likely to deteriorate.
- Si and amorphous SiO 2 are simultaneously deposited using a sputtering method (see, for example, Patent Document 1).
- an electron conductive material layer (carbon material) is provided on the surface of the SiO x particles (see, for example, Patent Document 2).
- the negative electrode active material layer is formed so as to contain Si and O and to increase the oxygen ratio on the side close to the negative electrode current collector (for example, Patent Document 3). reference.).
- the negative electrode active material layer contains Si and O, the total average oxygen content is 40 atomic% or less, and the average oxygen content is increased on the side closer to the negative electrode current collector.
- the difference between the average oxygen content on the side close to the negative electrode current collector and the average oxygen content on the side far from the negative electrode current collector is 4 atomic% to 30 atomic%.
- a nanocomposite containing a Si phase, SiO 2 and My 2 O metal oxide is used (for example, see Patent Document 5).
- a negative electrode active material represented by Li a SiO x (0.5 ⁇ ax ⁇ 1.1, 0.2 ⁇ x ⁇ 1.2) is used (for example, (See Patent Document 7).
- Li is deposited on an active material precursor containing Si and O.
- the composition of SiO x is controlled (see, for example, Patent Document 8).
- the molar ratio of the O amount to the Si amount in the negative electrode active material body is set to 0.1 to 1.2, and the O amount relative to the Si amount in the vicinity of the interface between the negative electrode active material body and the current collector is The difference between the maximum value and the minimum value of the molar ratio is set to 0.4 or less.
- a lithium-containing porous metal oxide Li x SiO: 2.1 ⁇ x ⁇ 4
- a hydrophobized layer such as a silane compound or a siloxane compound is formed on a thin film containing Si (see, for example, Patent Document 10).
- a conductive powder in which the surface of SiO x (0.5 ⁇ x ⁇ 1.6) is coated with a graphite film is used (see, for example, Patent Document 11).
- a broad peak appears at 1330 cm -1 and 1580 cm -1 in the Raman shift of the Raman spectra for graphite coating, their intensity ratio I 1330 / I 1580 and 1.5 ⁇ I 1330 / I 1580 ⁇ 3 It is said.
- the cumulative 90% diameter (D90) of the powder is 50 ⁇ m or less, and the particle diameter of the particles is less than 2 ⁇ m.
- SiO x (0.3 ⁇ x ⁇ 1.6) is used, and the electrode unit is pressurized at 3 kgf / cm 2 or more during charge / discharge (see, for example, Patent Document 13).
- a Si oxide having a Si: O atomic ratio of 1: y (0 ⁇ y ⁇ 2) is used (see, for example, Patent Document 14). .
- an amorphous metal oxide is provided on the surface of primary particles such as Si in order to accumulate or release a large amount of lithium ions electrochemically (see, for example, Patent Document 15).
- the Gibbs free energy at the time of metal oxidation for forming this metal oxide is smaller than the Gibbs free energy at the time of oxidation of Si or the like.
- a negative electrode active material having an alloy composition composed of two kinds of metals as a main component is used (for example, see Patent Document 16).
- the first metal has the property of occluding and releasing Li (such as Si), and the second metal has the property of stabilizing the shape change of the first metal when occluding and releasing Li. (Such as Fe).
- Patent Document 1 Japanese Patent Application Laid-Open No. 2001-185127 Patent Document 2: Japanese Patent Application Laid-Open No. 2002-042806 Patent Document 3: Japanese Patent Application Laid-Open No. 2006-164554 Patent Document 4: Japanese Patent Application Laid-Open No. 2006-114454 Patent Document 5: Japanese Patent Application Laid-Open No. 2006-114454 Japanese Patent Application Laid-Open No. 2009-070825 Patent Document 6: Japanese Patent Application Laid-Open No. 2008-282919 Patent Document 7: International Publication No. 2007/010922 Pamphlet Patent Document 8: Japanese Patent Application Laid-Open No. 2008-251369 Patent Document 9: Japanese Patent Application Laid-Open No.
- Patent Document 10 JP 2007-234255 A Patent Document 11: JP 2009-212074 A Patent Document 12: JP 2009-205950 A Patent Document 13: JP 2009-076373 A Patent Document 14: Patent No. Patent Document 15: Japanese Patent No. 2997441: JP 2009-1 4104 JP Patent Document 16: JP 2006-100244 JP
- An active material for a secondary battery includes a core part capable of occluding and releasing lithium ions and a low crystalline or non-crystalline substance provided on at least a part of the surface of the core part. And a covering portion.
- the core portion includes Si and O as constituent elements, the atomic ratio x (O / Si) of O to Si satisfies 0 ⁇ x ⁇ 0.5, and the covering portion includes Si and O as constituent elements.
- the atomic ratio y of O to (O / Si) satisfies 0.5 ⁇ y ⁇ 1.8.
- the covering portion has a void, and a carbon-containing material is provided in at least a part of the void.
- a secondary battery according to an embodiment of the present technology includes a positive electrode, a negative electrode including an active material, and an electrolytic solution, and the negative electrode uses the active material for a secondary battery according to the embodiment of the present technology described above. It is.
- An electronic device according to an embodiment of the present technology includes a secondary battery, and the secondary battery has a configuration similar to that of the secondary battery according to the embodiment of the present technology described above.
- low crystallinity means a non-crystalline region and a crystalline region (crystal grain) when the cross section or surface of the coating is observed using a high-angle scattering dark field scanning transmission electron microscope (HAADF STEM) or the like. Means a crystalline state in which both exist.
- non-crystalline is synonymous with so-called amorphous, and when a covering portion is observed using HAADF STEM or the like, only an amorphous region exists, and a crystalline region exists. It means a crystalline state that is not. Note that the magnification during observation is, for example, 1.2 ⁇ 10 6 times.
- the surface of the core portion is provided with a low crystalline or non-crystalline covering portion, and the core portion and the covering portion are respectively While having the above-described composition, a carbon-containing material is provided in the void of the covering portion. Therefore, excellent battery characteristics can be obtained. Moreover, the same effect can be acquired also in the electronic device of one Embodiment of this technique.
- FIG. 8 is a cross-sectional view taken along line VIII-VIII of the secondary battery shown in FIG. It is a top view which represents typically the structure of the positive electrode and negative electrode which were shown in FIG. It is sectional drawing showing the structure of the secondary battery (cylindrical type) of one Embodiment of this technique. It is sectional drawing which expands and represents a part of winding electrode body shown in FIG.
- FIG. 13 is a cross-sectional view taken along line XIII-XIII of the spirally wound electrode body illustrated in FIG.
- It is a block diagram showing the structure of the application example (battery pack) of a secondary battery.
- It is a block diagram showing the structure of the application example (electric vehicle) of a secondary battery.
- It is a block diagram showing the structure of the application example (electric power storage system) of a secondary battery.
- FIG. 1 illustrates a cross-sectional configuration of a negative electrode using a secondary battery active material according to an embodiment of the present technology.
- FIG. 2 illustrates a negative electrode active material that is a secondary battery active material according to an embodiment of the present technology. It represents the cross-sectional structure of the substance.
- 3 to 6 are HAADF STEM photographs (hereinafter, simply referred to as “TEM photographs”) of the cross-sectional structure of the negative electrode active material.
- the negative electrode has a negative electrode active material layer 2 on a negative electrode current collector 1 as shown in FIG.
- the negative electrode active material layer 2 may be provided on both sides of the negative electrode current collector 1 or may be provided only on one side. However, the negative electrode current collector 1 may not be provided.
- the negative electrode current collector 1 is formed of, for example, a conductive material excellent in electrochemical stability, electrical conductivity, and mechanical strength.
- the conductive material is, for example, a metal such as Cu, Ni, or stainless steel. Material. Among these, a material that does not form an intermetallic compound with Li and is alloyed with the negative electrode active material layer 2 is preferable.
- the negative electrode current collector 1 preferably contains C and S as constituent elements. This is because the physical strength of the negative electrode current collector 1 is improved, so that the negative electrode current collector 1 is hardly deformed even when the negative electrode active material layer 2 expands and contracts during charging and discharging.
- a negative electrode current collector 1 is, for example, a metal foil doped with C and S.
- the content of C and S is not particularly limited, but is preferably 100 ppm or less. This is because a higher effect can be obtained.
- the surface of the negative electrode current collector 1 (the surface in contact with the negative electrode active material layer 2) may be roughened or may not be roughened.
- the non-roughened negative electrode current collector 1 is, for example, a rolled metal foil, and the roughened negative electrode current collector 1 is, for example, a metal foil that has been subjected to electrolytic treatment or sandblasting. is there.
- the electrolytic treatment is a method of providing irregularities by forming fine particles on the surface of a metal foil or the like using an electrolytic method in an electrolytic bath.
- a metal foil produced by an electrolytic method is generally called an electrolytic foil (for example, an electrolytic Cu foil).
- the surface of the negative electrode current collector 1 is preferably roughened. This is because the anchor effect improves the adhesion of the negative electrode active material layer 2 to the negative electrode current collector 1.
- the surface roughness (for example, ten-point average roughness Rz) of the negative electrode current collector 1 is not particularly limited, but is preferably as large as possible in order to improve the adhesion of the negative electrode active material layer 2 by the anchor effect. However, if the surface roughness is too large, the adhesion of the negative electrode active material layer 2 may be lowered.
- the negative electrode active material layer 2 includes one or two or more particulate negative electrode active materials 200 that can occlude and release electrode reactants (lithium ions). Furthermore, other materials such as a negative electrode binder or a negative electrode conductive agent may be included.
- the negative electrode active material 200 includes a core part 201 capable of occluding and releasing lithium ions, and a covering part 202 provided on the surface of the core part 201.
- the state in which the core part 201 is covered with the covering part 202 in this way can be confirmed using, for example, a scanning electron microscope (SEM). Further, the crystallinity (crystal state) of the core part 201 and the covering part 202 can be confirmed using a TEM or the like as shown in FIGS.
- the core part 201 contains Si and O as constituent elements, and the atomic ratio x (O / Si) of O to Si satisfies 0 ⁇ x ⁇ 0.5. More specifically, the core portion 201 includes, for example, a silicon-based material (SiO x : 0 ⁇ x ⁇ 0.5). Compared to the case where the atomic ratio x is out of the range (x ⁇ 0.5), the core part 201 easily absorbs and releases lithium ions during charge and discharge, and the irreversible capacity decreases, so that a high battery capacity is obtained. Because it is.
- the crystallinity of the core part 201 may be any of high crystallinity, low crystallinity, or non-crystallinity. Among these, high crystallinity or low crystallinity is preferable, and high crystallinity is more preferable. This is because the core part 201 easily absorbs and releases lithium ions during charging and discharging, so that a high battery capacity and the like can be obtained. Moreover, it is because the core part 201 becomes difficult to expand and contract during charging and discharging. Especially, it is preferable that the half value width (2 (theta)) of the diffraction peak resulting from the (111) crystal plane of Si obtained by X-ray diffraction is 20 degrees or less. The crystallite size resulting from the (111) crystal plane of Si is preferably 10 nm or more. This is because a higher effect can be obtained.
- the core part 201 may contain any one type or two or more types of other elements together with Si and O.
- the core part 201 preferably contains Fe as a constituent element. This is because the electrical resistance of the core part 201 is lowered.
- the ratio of Fe to Si and O (Fe / (Si + O)) is not particularly limited, but is preferably 0.01% by weight to 7.5% by weight. This is because not only the electrical resistance of the core part 201 is lowered, but also the diffusibility of lithium ions is improved.
- Fe may exist separately from Si and O (in a free state), or may form an alloy or a compound with at least one of Si and O. The same applies to Al and the like described later.
- the state of the core portion 201 containing Fe can be confirmed using, for example, EDX.
- the core part 201 includes Al, Cr, Ni, B, Mg, Ca, Ti, V, Mn, Co, Cu, Ge, Y, Zr, Mo, Ag, In, Sn, Sb, Ta, W, At least one element of Pb, La, Ce, Pr, Nd, and the like may be included as a constituent element.
- at least one of Al, Ca, Mn, Cr, Mg, and Ni is preferable. This is because the electrical resistance of the core part 201 is lowered.
- the ratio of Al or the like to Si and O is not particularly limited.
- the diffusibility of lithium ion improves more.
- the average particle diameter (median diameter D50) of the core part 201 is not particularly limited, but is preferably 0.1 ⁇ m to 20 ⁇ m. This is because a higher effect can be obtained. Specifically, if D50 is too small, the surface area increases, which may lead to a decrease in safety. If D50 is too large, the negative electrode active material 200 may be damaged due to expansion during charging. there is a possibility. In addition, if D50 is too small, it may be difficult to apply the slurry containing the negative electrode active material 200.
- the covering portion 202 is provided on at least a part of the surface of the core portion 201. For this reason, the coating
- the covering portion 202 contains Si and O as constituent elements, and the atomic ratio y (O / Si) of O to Si satisfies 0.5 ⁇ y ⁇ 1.8. More specifically, the covering portion 202 includes, for example, a silicon-based material (SiO y : 0.5 ⁇ y ⁇ 1.8). This is because deterioration of the negative electrode active material 200 is suppressed even when charging and discharging are repeated. Thereby, the core part 201 is chemically and physically protected by the coating
- a silicon-based material SiO y : 0.5 ⁇ y ⁇ 1.8
- the covering portion 202 when the covering portion 202 is interposed between the core portion 201 and the electrolytic solution, the highly reactive core portion 201 is difficult to come into contact with the electrolytic solution, so that the decomposition reaction of the electrolytic solution is suppressed.
- the covering portion 202 if the covering portion 202 is formed of the same material as the core portion 201 (a material containing a common element (Si) as a constituent element), the adhesion of the covering portion 202 to the core portion 201 is also improved. Get higher.
- the covering portion 202 has flexibility (a property of being easily deformed), even when the core portion 201 expands and contracts during charging and discharging, the covering portion 202 easily expands and contracts (expands and contracts). As a result, the covering portion 202 is less likely to be damaged (ruptured or the like) when the core portion 201 is expanded and contracted, so that the covering state of the core portion 201 by the covering portion 202 is maintained even after repeated charge and discharge. Therefore, even if the core part 201 is cracked during charging and discharging, the new surface is difficult to be exposed and the new surface is difficult to contact the electrolytic solution, so that the decomposition reaction of the electrolytic solution is remarkably suppressed.
- the material for forming the covering portion 202 is a Si oxide (SiO y ).
- the crystallinity of the covering portion 202 is low crystalline or non-crystalline (amorphous). Compared with the case of high crystallinity, lithium ions are more easily diffused. Therefore, even when the surface of the core part 201 is covered with the covering part 202, the core part 201 can easily occlude and release lithium ions. Because.
- the crystallinity of the covering portion 202 is preferably lower (close to non-crystalline) than the crystalline state of the core portion 201, and more preferably non-crystalline. This is because the flexibility of the covering portion 202 is improved, so that the covering portion 202 can easily follow the expansion and contraction of the core portion 201 during charging and discharging. In addition, since the covering portion 202 is less likely to trap lithium ions, the entry and exit of lithium ions in the core portion 201 is less likely to be inhibited. Note that “the crystallinity of the covering portion 202 is lower than the crystallinity of the core portion 201” means that, for example, when the core portion 201 is highly crystalline, the covering portion 202 is low crystalline or non-crystalline. It means that there is. Or, for example, when the core part 201 is low crystalline, it means that the covering part 202 is non-crystalline.
- FIGS. 3 and 6 show a case where the core portion 201 is made of highly crystalline Si and the covering portion 202 is made of amorphous SiO y .
- FIGS. 4 and 5 show a case where the core portion 201 is made of high crystalline Si and the covering portion 202 is made of low crystalline SiO y .
- “Low crystallinity” means a crystalline state including both an amorphous region and a crystalline region (crystal grain), and is different from “noncrystalline” including only an amorphous region.
- the covering portion 202 may be observed using, for example, the above-described HAADF STEM. If it can be confirmed from the TEM photograph that a non-crystalline region and a crystalline region are mixed, the covering portion 202 has low crystallinity. Note that in the case where a non-crystalline region and a crystalline region are mixed, the crystalline region is observed as a region (crystal grain) having a granular contour. Since a stripe pattern (crystal lattice stripe) due to crystallinity is observed inside the crystal grain, the crystal grain can be identified from the amorphous region.
- non-crystalline and low crystalline are apparent from the TEM photographs shown in FIGS.
- the covering portion 202 is non-crystalline, as shown in FIG. 3, only the non-crystalline region is observed, and the crystalline region (crystal grains having crystal lattice stripes) is not observed.
- the covering portion 202 has low crystallinity, as shown in FIG. 4, it is observed that crystal grains (portions indicated by arrows) are scattered in the amorphous region. Is done. Since these crystal grains have crystal lattice stripes with a predetermined interval corresponding to the lattice plane interval d of Si, they are clearly distinguished from the surrounding amorphous regions. Note that when the TEM photograph shown in FIG. 4 was Fourier transformed (a figure corresponding to an electron diffraction diagram was obtained), the spots were arranged in a ring shape, so that a large number of crystal regions existed inside the covering portion 202. It was confirmed that
- the degree of low crystallinity of the covering portion 202 is not particularly limited, but among them, the average area occupation ratio of crystal grains due to the (111) face and the (220) face of Si is preferably 35% or less, More preferably, it is 25% or less, and more preferably 20% or less. This is because a higher effect can be obtained.
- the area occupation ratio (%) (sum of crystal grain area / area of observation area) ⁇ 100 is calculated.
- the drawing of the outline and the calculation of the area occupancy may be performed manually or mechanically using dedicated processing software.
- an average value of the area occupancy rates (average area occupancy rate) calculated in each area is calculated.
- the covering portion 202 is equally divided in the thickness direction, and the area is occupied by 20 areas in the inner portion and the outer portion. It is preferable to calculate the rate.
- the average grain size of the crystal grains is not particularly limited, but is preferably 55 nm or less, and more preferably 50 nm or less. This is because a higher effect can be obtained.
- This average particle size calculation procedure is to calculate the average area occupancy rate except for calculating the average particle size for each area and then calculating the average value of the average particle size (final average particle size) It is the same.
- the diameter be the particle size.
- the calculation of the particle size may be artificial or mechanical as in the case of calculating the average area occupancy.
- the average area occupancy may be the same or different between the inner portion and the outer portion.
- the average area occupation ratio of the crystal grains in the inner part is preferably equal to or larger than the average area occupation ratio of the crystal grains in the outer part (average area occupation ratio of the inner part ⁇ average of the outer part) Area occupancy). This is because a higher effect can be obtained.
- the average thickness of the covering portion 202 is not particularly limited, but is preferably as thin as possible and more preferably 1 nm to 3000 nm. This is because the core part 201 can easily absorb and release lithium ions, and the protective function by the covering part 202 is effectively exhibited. Specifically, if the average thickness is less than 1 nm, the covering portion 202 may be difficult to protect the core portion 201. On the other hand, if the average thickness is greater than 3000 nm, the electrical resistance increases, and the core part 201 may not be able to occlude and release lithium ion ions during charging and discharging. This is because when the material for forming the covering portion 202 is SiO y , the SiO y has a property of easily occluding lithium ions but hardly releasing the lithium ions once occluded.
- the average thickness of the covering portion 202 is calculated by the following procedure. First, one negative electrode active material 200 is observed using SEM or the like. The magnification at the time of observation is preferably such a magnification that the boundary between the core portion 201 and the covering portion 202 can be visually confirmed (determined) in order to measure the thickness T of the covering portion 202. Subsequently, after measuring the thickness T of the covering portion 202 at arbitrary 10 points, the average value (average thickness T per piece) is calculated. In this case, it is preferable to set the measurement positions so that they are widely dispersed without concentrating around a specific place as much as possible. Subsequently, the above average value calculation operation is repeated until the total number of observations by SEM reaches 100. Finally, the average value (average thickness T per one) calculated for the 100 negative electrode active materials 200 is calculated, and the average thickness of the covering portion 202 is calculated. To do.
- the average coverage of the covering portion 202 with respect to the core portion 201 is not particularly limited, but is preferably as large as possible, and more preferably 30% or more (30% to 100%). This is because the protective function of the covering portion 202 is further improved.
- the above-described coverage calculation operation is repeated until the total number of observations by SEM reaches 100.
- the average value of the coverage ratio (coverage ratio per one) calculated for 100 negative electrode active materials 200 is calculated as the average coverage ratio of the covering portion 202.
- the covering portion 202 is preferably adjacent to the core portion 201, but a natural oxide film (SiO 2 ) may be interposed between the core portion 201 and the covering portion 202.
- the natural oxide film is formed by oxidizing the vicinity of the surface layer of the core portion 201 in the atmosphere. If the core part 201 exists in the center of the negative electrode active material 200 and the covering part 202 exists outside, the presence of the natural oxide film hardly affects the functions of the core part 201 and the covering part 202.
- the negative electrode active material 200 includes the core portion 201 and the covering portion 202
- XPS X-ray photoelectron spectroscopy
- EDX energy dispersive X-ray
- the negative electrode active material 200 may be analyzed using an analysis method (EDX) or the like.
- the composition of the core part 201 and the covering part 202 can be confirmed by measuring the oxidation degree (atoms x, y) of the central part and the surface layer part of the negative electrode active material 200.
- the covering part 202 may be dissolved and removed using an acid such as HF.
- the detailed procedure for measuring the degree of oxidation is, for example, as follows. First, the negative electrode active material 200 (the core portion 201 covered with the covering portion 202) is quantified using a combustion method, and the total Si amount and O amount are calculated. Subsequently, after the covering portion 202 is washed and removed using HF or the like, the core portion 202 is quantified using a combustion method to calculate the Si amount and the O amount. Finally, the Si amount and O amount of the covering portion 202 are calculated by subtracting the Si amount and O amount of the core portion 201 from the total Si amount and O amount. Thereby, since Si amount and O amount are specified regarding the core part 201 and the coating
- the plurality of negative electrode active materials 200 may be separated (dispersed) from each other, or two or more of them may be in contact (or connected).
- the positional relationship of the negative electrode active materials 200 may be arbitrary.
- coated part 202 may contain at least 1 sort (s) of elements, such as Fe, Al, and Ca, as a structural element. This is because the electrical resistance of the covering portion 202 decreases.
- the ratio of Fe or the like to Si and O (Fe etc./(Si+O)) is not particularly limited.
- the covering portion 202 has one or more voids therein, and a material (carbon-containing material) containing C as a constituent element is provided in at least a part of the voids. That is, the carbon-containing material is inserted into the gap, and the gap is filled with the carbon-containing material. This is because the conductivity of the negative electrode active material 200 is improved and the decomposition reaction of the electrolytic solution is suppressed without hindering the expansion / contraction properties of the covering portion 202 following the expansion / contraction of the core portion 201 described above.
- the voids present inside the coating portion 202 are used as a space for relaxing internal stress generated when the negative electrode active material 200 expands and contracts during charging and discharging. For this reason, when the coating
- the void exposes the highly reactive coating portion 202 therein, so that the electrolytic solution is easily decomposed on the exposed surface. In this regard, if a carbon-containing material is provided in the gap, the highly reactive coating 202 is difficult to be exposed inside the gap, so that the decomposition reaction of the electrolytic solution is suppressed.
- the carbon-containing material since carbon is excellent in deformability (flexibility) and high conductivity, the carbon-containing material hardly inhibits the expansion / contraction property of the covering portion 202 that follows the expansion / contraction of the core portion 201 and the carbon-containing material. The electrical conductivity of the covering portion 202 containing the is improved.
- the carbon-containing material may contain only C as a constituent element, or may contain any one kind or two or more kinds of other elements together with C.
- the type of the “other element” is not particularly limited, and is, for example, H or O.
- a G band peak derived from a graphite structure is detected in the vicinity of 1590 cm ⁇ 1 in the Raman spectrum, and a D band derived from a defect.
- a peak is detected around 1350 cm ⁇ 1 .
- the ratio IG / ID between the intensity IG of the G band peak and the intensity ID of the D band peak is also called a G / D ratio, and is an index representing the crystallinity (purity) of the carbon material.
- the ratio IG / ID of the carbon-containing material provided in the gap of the covering portion 202 is not particularly limited, but is preferably 0.3 to 3. This is because excellent binding properties, conductivity, and deformability can be obtained.
- the ratio IG / ID is smaller than 0.3, the binding property is increased, and thus the adhesion between the carbon-containing materials and the adhesion of the carbon-containing material to the covering portion 202 are improved.
- the conductivity decreases and becomes hard, the carbon-containing material hardly expands and contracts following the expansion and contraction of the covering portion 202, and sufficient conductivity may not be obtained.
- the ratio IG / ID is greater than 3, the conductivity becomes high and the softness is increased, so that the carbon-containing material easily expands and contracts following the expansion and contraction of the covering portion 202 and sufficient conductivity is obtained. .
- the binding property is reduced, the adhesion between the carbon-containing materials and the adhesion of the carbon-containing material to the covering portion 202 may be reduced.
- the ratio IG / ID is 0.3 to 3
- the binding property and conductivity of the carbon-containing material are increased, and the carbon-containing material is expanded and contracted following the expansion and contraction of the covering portion 202. It becomes easy to do.
- the formation factor of the void is not particularly limited. This is because, if a void exists in the covering portion 202 regardless of what factor is formed, the void can function as a space for stress relaxation. Further, the void distribution in the covering portion 202 is not particularly limited, but among them, the maximum peak void diameter in the void distribution of the covering portion 202 measured by the nitrogen adsorption method and the mercury intrusion method is preferably 500 nm or less. More preferably, it is 50 nm or less. This is because, if the void diameter is too large, the occupied volume of Si in the covering portion 202 decreases, so that the amount of occluded and released lithium ions decreases (battery capacity decreases).
- any method for measuring the void distribution of the covering portion 202 any method can be used according to the size of the void diameter.
- a nitrogen adsorption method or the like is used for a void distribution having a void diameter of 3 nm or more
- a mercury intrusion method or the like is used for a void distribution having a void diameter of 100 nm or more.
- This mercury porosimeter is, for example, Autopore IV9500 manufactured by Shimadzu Corporation.
- an automatic specific surface area / pore distribution measuring device such as Tristar 3000 manufactured by Shimadzu Corporation is used.
- the covering portion 202 may be a single layer or a multilayer, but among them, a multilayer is preferable as shown in FIG. This is because a stress relaxation space (void) is easily formed in the covering portion 202 (interlayer).
- the broken line shown in FIG. 6 represents the standard of the boundary of each layer.
- the covering portion 202 may be multi-layered over the entire surface, or may be partially multi-layered.
- a carbon-containing layer may be provided on the surface of the negative electrode active material 200.
- This carbon-containing layer is provided on at least a part of the surface of the negative electrode active material 200 and preferably has an electric resistance lower than that of the core part 201 and the covering part 202. This is because the core part 201 is less likely to come into contact with the electrolytic solution, so that the decomposition reaction of the electrolytic solution is suppressed. Moreover, it is because the electrical resistance of the negative electrode active material 200 falls more.
- the composition of the carbon-containing layer is the same as that of the carbon-containing material described above. That is, the carbon-containing layer contains C as a constituent element, and may further contain one or more other elements (for example, H or O) as necessary. However, the material for forming the carbon-containing layer may be the same as or different from the material for forming the carbon-containing material. Specific examples of the carbon-containing layer include a carbon material described later as “another negative electrode active material”. When the material for forming the carbon-containing layer is the same as the material for forming the carbon-containing material, the gap of the covering portion 202 is filled with a part of the carbon-containing layer instead of the carbon-containing material. May be sealed. This is because the carbon-containing material and the carbon-containing layer can be formed substantially collectively.
- the average thickness of the carbon-containing layer is not particularly limited, but is preferably 500 nm or less, and more preferably 200 nm or less. Moreover, the average coverage of the carbon-containing layer with respect to the negative electrode active material 200 is not particularly limited, but is preferably 30% or more. This is because a higher effect can be obtained. In particular, when the average thickness is greater than 500 nm, the properties of the slurry containing the negative electrode active material 200 are deteriorated, which may make it difficult to apply the slurry. Note that details regarding the calculation procedure of the average coverage and average thickness of the carbon-containing layer are the same as those of the covering portion 202.
- the negative electrode binder contains, for example, any one kind or two kinds or more of synthetic rubber or polymer material.
- the synthetic rubber include styrene butadiene rubber, fluorine rubber, and ethylene propylene diene.
- the polymer material include polyvinylidene fluoride, polyimide, polyamide, polyamideimide, polyacrylic acid, lithium polyacrylate, sodium polyacrylate, polymaleic acid, and copolymers thereof.
- the polymer material may be, for example, carboxymethyl cellulose, styrene butadiene rubber, or polyvinyl alcohol.
- the negative electrode conductive agent contains one or more of carbon materials such as graphite, carbon black, acetylene black, and ketjen black.
- the negative electrode conductive agent may be a metal material or a conductive polymer as long as it is a conductive material.
- the negative electrode active material layer 2 may contain other types of negative electrode active materials together with the negative electrode active material 200 including the core part 201 and the covering part 202 as necessary.
- This “other negative electrode active material” is, for example, a carbon material. This is because the electrical resistance of the negative electrode active material layer 2 is lowered and the negative electrode active material layer 2 is less likely to expand and contract during charge / discharge.
- This carbon material is, for example, graphitizable carbon, non-graphitizable carbon having a (002) plane spacing of 0.37 nm or more, or graphite having a (002) plane spacing of 0.34 nm or less.
- pyrolytic carbons, cokes, glassy carbon fibers, organic polymer compound fired bodies, activated carbon or carbon blacks include pitch coke, needle coke, petroleum coke and the like.
- the organic polymer compound fired body is obtained by firing and carbonizing a phenol resin, a furan resin, or the like at an appropriate temperature.
- the shape of the carbon material may be any of fibrous, spherical, granular or scale-like.
- the other negative electrode active material may be a metal oxide or a polymer compound.
- the metal oxide include iron oxide, ruthenium oxide, and molybdenum oxide.
- the polymer compound include polyacetylene, polyaniline, and polypyrrole.
- the negative electrode active material layer 2 is formed by, for example, a coating method, a firing method (sintering method), or two or more kinds thereof.
- the application method is, for example, a method in which a negative electrode active material is mixed with a negative electrode binder and then dispersed in an organic solvent and applied.
- the firing method is, for example, a method in which heat treatment is performed at a temperature higher than the melting point of the negative electrode binder or the like after being applied by the same procedure as the application method.
- a known method can be used as the firing method. For example, an atmosphere firing method, a reaction firing method, a hot press firing method, or the like.
- This negative electrode is manufactured, for example, by the following procedure.
- the description is abbreviate
- a particulate (powdered) core portion 201 containing Si and O as constituent elements is obtained by using, for example, a gas atomizing method, a water atomizing method, a melt pulverizing method, or the like.
- the core part 201 contains a metal element such as Fe, the metal material is melted together with the raw materials.
- a coating portion 202 containing Si and O as constituent elements is formed on the surface of the core portion 201 using, for example, a vapor phase growth method such as a vapor deposition method or a sputtering method.
- a vapor phase growth method such as a vapor deposition method or a sputtering method.
- the covering portion 202 tends to become non-crystalline.
- the deposition process may be performed while heating, or the coating part 202 may be made low crystalline by heating after the coating part 202 is formed.
- the degree of low crystallinity is controlled according to conditions such as temperature and time during heating, for example.
- the core portion 201 is rotated as necessary, and an opening / closing mechanism such as a shutter is used to control whether or not the deposition process is performed. It is preferable to perform a deposition process on the surface of the portion 201. This is because the surface of the core part 201 is easily covered uniformly by the covering part 202. In addition, since the covering portion 202 has multiple layers, stress relaxation spaces (voids) are easily formed between the layers.
- a carbon-containing material is formed in the voids of the covering portion 202 using a thermal decomposition chemical vapor deposition (CVD) method or the like.
- CVD thermal decomposition chemical vapor deposition
- methane, ethane, ethylene, acetylene, propane, or the like is used as the carbon source (organic gas).
- the thermal decomposition CVD method since the carbon source reaches the inside of the fine voids and is thermally decomposed, the fine voids can be easily filled with the carbon-containing material.
- the structure in which the carbon-containing material is embedded in the minute voids of the covering portion 202 is realized for the first time by forming the carbon-containing material separately from the covering portion 202 by using a thermal decomposition CVD method or the like as described above.
- the forming material of the covering portion 202 and the forming material of the carbon-containing material are co-evaporated, or when the carbon-containing material is formed using the vapor deposition method after forming the covering portion 202, The characteristic structure cannot be obtained. This is because the carbon-containing material cannot be selectively formed so as to fill the voids of the covering portion 202.
- the core part 201 is covered with the covering part 202 and the carbon-containing material is inserted into the gap of the covering part 202, so that the negative electrode active material 200 is obtained.
- a carbon-containing layer may be formed on the surface of the covering portion 202 using a vapor deposition method or a wet coating method.
- the vapor phase growth method include a vapor deposition method, a sputtering method, a thermal decomposition CVD method, a thermal decomposition CVD method, an electron beam evaporation method, and a sugar carbonization method.
- the thermal decomposition CVD method is preferable. This is because the carbon-containing layer is easily formed to have a uniform thickness.
- the voids of the covering portion 202 are sealed with a carbon-containing layer instead of the carbon-containing material, a part of the carbon-containing layer can be embedded in the fine voids.
- the carbon-containing layer is formed by spraying steam directly on the surface of the negative electrode active material.
- the carbon-containing layer is formed using a powder sputtering method while introducing Ar gas.
- the CVD method for example, a gas obtained by sublimating a metal chloride and a mixed gas such as H 2 and N 2 are mixed so that the molar ratio of the metal chloride is 0.03 to 0.3. After that, it is heated to 1000 ° C. or higher to form a carbon-containing layer.
- a metal-containing solution for example, after adding a metal-containing solution to a slurry containing a negative electrode active material to form a metal hydroxide by adding an alkali solution, reduction treatment with hydrogen at 450 ° C. is performed. A carbon-containing layer is formed on the surface of the negative electrode active material.
- a carbon material is used as a material for forming the carbon-containing layer
- a negative electrode active material is introduced into the chamber, an organic gas is introduced into the chamber, and then heat treatment is performed under conditions of 10,000 Pa and 1000 ° C. or higher.
- a time is performed to form a carbon-containing layer on the surface of the negative electrode active material.
- the type of the organic gas is not particularly limited as long as it generates carbon by thermal decomposition, and examples thereof include methane, ethane, ethylene, acetylene, and propane.
- the negative electrode active material 200 and another material such as a negative electrode binder are mixed to form a negative electrode mixture, and then dissolved in a solvent such as an organic solvent to obtain a negative electrode mixture slurry.
- the negative electrode mixture slurry is applied to the surface of the negative electrode current collector 1 and then dried to form the negative electrode active material layer 2. Thereafter, the negative electrode active material layer 2 may be compression-molded and heated (fired) as necessary.
- the negative electrode active material 200 has a low crystalline or non-crystalline covering portion 202 on the surface of the core portion 201, and the core portion 201 and the covering portion 20 have the above-described composition. is doing.
- a carbon-containing material is provided in the gap of the covering portion 202.
- the conductivity of the negative electrode active material 200 is improved, and the decomposition reaction of the electrolytic solution due to the highly reactive coating portion 202 is suppressed. Therefore, it can contribute to the performance improvement of the secondary battery using a negative electrode active material or a negative electrode.
- the ratio IG / ID of the carbon-containing material measured by the Raman spectrum method is 0.3 to 3, or the maximum peak void diameter in the pore distribution of the coating measured by the nitrogen adsorption method and the mercury intrusion method If it is 500 nm or less, a higher effect can be acquired.
- the covering portion 202 is a multilayer, a stress relaxation gap is easily formed in the covering portion 202, so that a higher effect can be obtained.
- a carbon-containing layer is provided on the surface of the negative electrode active material 200, the average thickness of the carbon-containing layer is 500 nm or less, or the average coverage of the carbon-containing layer with respect to the negative electrode active material 200 is 30% or more. If so, a higher effect can be obtained.
- the negative electrode active material 200 provided with the carbon-containing layer can be easily formed by sealing the gap of the covering portion 202 with a part of the carbon-containing layer.
- the covering portion 202 has low crystallinity, and the average area occupancy of crystal grains due to the Si (111) plane and (220) plane is 35% or less, or the average grain diameter of the crystal grains is 55 nm or less. Therefore, a higher effect can be obtained.
- the average area occupancy and the average grain size in the inner part of the crystal grains are the same as the average area occupancy and the average grain diameter in the outer part, or If it is larger, a higher effect can be obtained.
- the average coverage of the covering portion 202 with respect to the core portion 201 is 30% or more, or the average thickness of the covering portion 202 is 1 nm to 3000 nm, a higher effect can be obtained.
- the core part 201 contains Fe as a constituent element and the ratio of Fe to Si and O (Fe / (Si + O)) is 0.01 wt% to 7.5 wt%, a higher effect can be obtained. Can do.
- FIG. 8 shows a cross section taken along the line VIII-VIII shown in FIG.
- FIG. 9 schematically shows a planar configuration of the positive electrode 21 and the negative electrode 22 shown in FIG.
- the rectangular secondary battery is mainly one in which the battery element 20 is housed inside the battery can 11.
- the battery element 20 is a wound laminate in which a positive electrode 21 and a negative electrode 22 are laminated and wound via a separator 23, and has a flat shape according to the shape of the battery can 11.
- the battery can 11 is, for example, a square exterior member. As shown in FIG. 8, this rectangular exterior member has a rectangular or substantially rectangular shape (including a curve in part) in the longitudinal section, and is not only a rectangular shape but also an oval shape. This also applies to the square battery. That is, the square-shaped exterior member is a bottomed rectangular or bottomed oval shaped container-like member having a rectangular shape or a substantially rectangular (oval shape) opening formed by connecting arcs with straight lines. FIG. 8 shows a case where the battery can 11 has a rectangular cross-sectional shape.
- the battery can 11 is made of a conductive material such as Fe, Al, or an alloy thereof, and may function as an electrode terminal.
- Fe that is harder than Al is preferable in order to suppress swelling of the battery can 11 by utilizing hardness (hardness to deform) during charge and discharge.
- the battery can 11 is made of Fe, Ni or the like may be plated on the surface.
- the battery can 11 has a hollow structure in which one end is opened and the other end is closed, and is sealed by an insulating plate 12 and a battery lid 13 attached to the open end.
- the insulating plate 12 is provided between the battery element 20 and the battery lid 13 and is formed of an insulating material such as polypropylene.
- the battery lid 13 is formed of, for example, the same material as the battery can 11 and may function as an electrode terminal similarly to the battery can 11.
- a terminal plate 14 serving as a positive electrode terminal is provided outside the battery lid 13, and the terminal plate 14 is electrically insulated from the battery lid 13 through an insulating case 16.
- the insulating case 16 is made of an insulating material such as polybutylene terephthalate, for example.
- a through hole is provided at substantially the center of the battery lid 13, and the through hole is electrically connected to the terminal plate 14 and is electrically insulated from the battery lid 13 through the gasket 17.
- a positive electrode pin 15 is inserted.
- the gasket 17 is formed of, for example, an insulating material, and asphalt may be applied to the surface of the gasket 17.
- a cleavage valve 18 and an injection hole 19 are provided in the vicinity of the periphery of the battery lid 13.
- the cleavage valve 18 is electrically connected to the battery lid 13 and is disconnected from the battery lid 13 when the internal pressure of the battery exceeds a certain level due to an internal short circuit or heating from the outside. Is to be released.
- the injection hole 19 is closed by a sealing member 19A made of, for example, a stainless steel ball.
- a positive electrode lead 24 made of a conductive material such as Al is attached to an end portion (for example, an inner terminal portion) of the positive electrode 21, and Ni or the like is attached to an end portion (for example, the outer terminal portion) of the negative electrode 22.
- a negative electrode lead 25 made of a conductive material is attached.
- the positive electrode lead 24 is welded to one end of the positive electrode pin 15 and electrically connected to the terminal plate 14, and the negative electrode lead 25 is welded to the battery can 11 and electrically connected to the battery can 11. It is connected.
- the positive electrode 21 includes, for example, a positive electrode active material layer 21B on both surfaces of the positive electrode current collector 21A.
- the positive electrode active material layer 21B may be provided only on one surface of the positive electrode current collector 21A.
- the positive electrode current collector 21A is formed of a conductive material such as Al, Ni, or stainless steel, for example.
- the positive electrode active material layer 21B includes one or more positive electrode materials capable of occluding and releasing lithium ions as a positive electrode active material, and a positive electrode binder or a positive electrode conductive agent is used as necessary. Other materials may be included.
- a positive electrode binder or a positive electrode electrically conductive agent is the same as that of the negative electrode binder and negative electrode electrically conductive agent which were already demonstrated, for example.
- a lithium-containing compound is preferable. This is because a high energy density can be obtained.
- the lithium-containing compound include a composite oxide containing Li and a transition metal element as constituent elements, and a phosphate compound containing Li and a transition metal element as constituent elements.
- the transition metal element is preferably one or more of Co, Ni, Mn, and Fe. This is because a higher voltage can be obtained.
- the chemical formula is represented by, for example, Li x M11O 2 or Li y M12PO 4 . In the formula, M11 and M12 represent one or more transition metal elements.
- x and y vary depending on the charge / discharge state, but are generally 0.05 ⁇ x ⁇ 1.10 and 0.05 ⁇ y ⁇ 1.10. In particular, when the positive electrode material contains Ni or Mn, the volume stability tends to be improved.
- the composite oxide containing Li and a transition metal element is, for example, Li x CoO 2 , Li x NiO 2 (x is an arbitrary value), or a lithium nickel composite oxide represented by the following formula (1) It is.
- the phosphate compound containing Li and a transition metal element include LiFePO 4 or LiFe 1-u Mn u PO 4 (u ⁇ 1). This is because high battery capacity is obtained and excellent cycle characteristics are also obtained.
- the positive electrode material may be a material other than the above. For example, a material represented by Li x M14 y O 2 (M14 is Ni and at least one of M13 shown in Formula (1), and x> 1 and y is arbitrary). Etc.
- LiNi 1-x M13 x O 2 (1) (M13 is Co, Mn, Fe, Al, V, Sn, Mg, Ti, Sr, Ca, Zr, Mo, Tc, Ru, Ta, W, Re, Y, Cu, Zn, Ba, B, Cr, Si. , Ga, P, Sb and Nb, and x satisfies 0.005 ⁇ x ⁇ 0.5.)
- examples of the positive electrode material include oxides, disulfides, chalcogenides, and conductive polymers.
- oxides include titanium oxide, vanadium oxide, and manganese dioxide.
- examples of the disulfide include titanium disulfide and molybdenum sulfide.
- An example of the chalcogenide is niobium selenide.
- examples of the conductive polymer include sulfur, polyaniline, and polythiophene.
- the negative electrode 22 has the same configuration as the negative electrode described above.
- the negative electrode 22 has a negative electrode active material layer 22B on both surfaces of the negative electrode current collector 22A.
- the configurations of the negative electrode current collector 22A and the negative electrode active material layer 22B are the same as the configurations of the negative electrode current collector 1 and the negative electrode active material layer 2, respectively.
- the chargeable capacity of the negative electrode material capable of occluding and releasing lithium ions is preferably larger than the discharge capacity of the positive electrode 21. This is to prevent Li metal from unintentionally precipitating during charge / discharge.
- the positive electrode active material layer 21B is provided, for example, on a part of the surface of the positive electrode current collector 21A (for example, a central region in the longitudinal direction).
- the negative electrode active material layer 22B is provided on the entire surface of the negative electrode current collector 22A, for example.
- the negative electrode active material layer 22B is provided in a region (opposing region R1) facing the positive electrode active material layer 21B and a region not facing (non-facing region R2) of the negative electrode current collector 22A.
- the portion provided in the facing region R1 is involved in charging / discharging, but the portion provided in the non-facing region R2 is hardly involved in charging / discharging.
- the positive electrode active material layer 21B and the negative electrode active material layer 22B are shaded.
- the negative electrode active material 200 (see FIG. 2) included in the negative electrode active material layer 22B includes the core portion 201 and the covering portion 202.
- the formation state of the core part 201 and the covering part 202 is changed from the state when the negative electrode active material layer 22B is formed. Can vary. However, in the non-facing region R2, it is hardly affected by charging / discharging, and the formation state of the negative electrode active material layer 22B is maintained.
- the negative electrode active material layer 22B in the non-facing region R2 Is preferably examined. This is because the state of the core portion 201 and the covering portion 202 can be accurately examined with good reproducibility without depending on the charge / discharge history (the presence / absence and number of times of charge / discharge).
- the maximum utilization rate of the negative electrode 22 in a fully charged state (hereinafter, simply referred to as “negative electrode utilization rate”) is not particularly limited, and can be arbitrarily set according to the ratio between the capacity of the positive electrode 21 and the capacity of the negative electrode 22. is there.
- X is the amount of occlusion of lithium ions per unit area when the negative electrode 22 is fully charged
- Y is the amount of lithium ions that can be occluded electrochemically per unit area of the negative electrode 22.
- the occlusion amount X can be obtained, for example, by the following procedure. First, after charging the secondary battery until it is fully charged, the secondary battery is disassembled, and a portion (inspection negative electrode) of the negative electrode 22 facing the positive electrode 21 is cut out. Subsequently, an evaluation battery using metal lithium as a counter electrode is assembled using the inspection negative electrode. Finally, after discharging the evaluation battery and measuring the discharge capacity at the first discharge, the storage capacity X is calculated by dividing the discharge capacity by the area of the inspection negative electrode. “Discharge” in this case means energization in the direction in which lithium ions are released from the inspection negative electrode. For example, until the battery voltage reaches 1.5 V at a current density of 0.1 mA / cm 2. Discharge constant current.
- the charge capacity is measured, and then the charge capacity is divided by the area of the inspection negative electrode. calculate.
- “Charging” in this case means that the inspection negative electrode is energized in the direction in which lithium ions are occluded.
- the current density is 0.1 mA / cm 2 and the battery voltage is 0 V. The voltage charging is performed until the current density reaches 0.02 mA / cm 2 .
- the negative electrode utilization rate is preferably 35% to 80%. This is because excellent initial charge / discharge characteristics, cycle characteristics, load characteristics, and the like can be obtained.
- the separator 23 separates the positive electrode 21 and the negative electrode 22 and allows lithium ions to pass through while preventing a short circuit of current due to contact between the two electrodes.
- the separator 23 is a porous film made of, for example, a synthetic resin or ceramic, and may be a laminated film in which two or more kinds of porous films are laminated.
- the synthetic resin is, for example, polytetrafluoroethylene, polypropylene, or polyethylene.
- the separator 23 is impregnated with an electrolytic solution that is a liquid electrolyte.
- This electrolytic solution is obtained by dissolving an electrolyte salt in a solvent, and may contain other materials such as additives as necessary.
- the solvent includes, for example, any one or more of nonaqueous solvents such as organic solvents.
- nonaqueous solvent include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ⁇ -butyrolactone, ⁇ -valerolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2 -Methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, butyric acid Methyl, methyl isobutyrate, methyl trimethylacetate, ethyl trimethylacetate, acetonitrile
- At least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate is preferable. This is because more excellent characteristics can be obtained.
- a high viscosity (high dielectric constant) solvent such as ethylene carbonate or propylene carbonate (for example, a relative dielectric constant ⁇ ⁇ 30) and a low viscosity solvent such as dimethyl carbonate, ethyl methyl carbonate or diethyl carbonate (for example, viscosity ⁇ 1 mPas).
- -A combination with s is more preferred. This is because the dissociation property of the electrolyte salt and the ion mobility are improved.
- the solvent preferably contains an unsaturated carbon bond cyclic carbonate.
- An unsaturated carbon bond cyclic ester carbonate is a cyclic ester carbonate containing one or more unsaturated carbon bonds (in which an unsaturated carbon bond is introduced at any position).
- Examples of the unsaturated carbon-bonded cyclic carbonate include vinylene carbonate, vinyl ethylene carbonate, and methylene ethylene carbonate.
- the content of the unsaturated carbon bond cyclic carbonate in the solvent is not particularly limited, but is, for example, 0.01 wt% to 10 wt%.
- the solvent preferably contains at least one of a halogenated chain carbonate and a halogenated cyclic carbonate. This is because a stable coating is formed on the surface of the negative electrode 22 during charging and discharging, so that the decomposition reaction of the electrolytic solution is suppressed.
- the halogenated chain carbonate ester is a chain carbonate ester containing halogen as a constituent element (at least one hydrogen is replaced by a halogen).
- the halogenated cyclic carbonate is a cyclic carbonate containing halogen as a constituent element (at least one hydrogen is replaced by a halogen).
- the kind of halogen is not particularly limited, but among them, F, Cl or Br is preferable, and F is more preferable. This is because an effect higher than that of other halogens can be obtained.
- the number of halogens is preferably two rather than one, and may be three or more. This is because the ability to form a protective film increases and a stronger and more stable coating is formed, so that the decomposition reaction of the electrolytic solution is further suppressed.
- the halogenated chain carbonate ester is, for example, fluoromethyl methyl carbonate, bis (fluoromethyl) carbonate or difluoromethyl methyl carbonate.
- the halogenated cyclic carbonate is 4-fluoro-1,3-dioxolan-2-one or 4,5-difluoro-1,3-dioxolan-2-one.
- This halogenated cyclic carbonate includes geometric isomers.
- the content of the halogenated chain carbonate and the halogenated cyclic carbonate in the solvent is not particularly limited, but is, for example, 0.01% by weight to 50% by weight.
- the solvent preferably contains sultone (cyclic sulfonate ester). This is because the chemical stability of the electrolytic solution is improved.
- the sultone is, for example, propane sultone or propene sultone.
- the content of sultone in the solvent is not particularly limited, and is, for example, 0.5% by weight to 5% by weight.
- the solvent preferably contains an acid anhydride.
- the acid anhydride include carboxylic acid anhydride, disulfonic acid anhydride, and carboxylic acid sulfonic acid anhydride.
- the carboxylic acid anhydride include succinic anhydride, glutaric anhydride, and maleic anhydride.
- the disulfonic anhydride include ethanedisulfonic anhydride and propanedisulfonic anhydride.
- the carboxylic acid sulfonic acid anhydride include anhydrous sulfobenzoic acid, anhydrous sulfopropionic acid, and anhydrous sulfobutyric acid.
- the content of the acid anhydride in the solvent is not particularly limited, but is, for example, 0.5% by weight to 5% by weight.
- the electrolyte salt includes, for example, any one or more of light metal salts such as lithium salts.
- the lithium salt include LiPF 6 , LiBF 4 , LiClO 4 , LiAsF 6 , LiB (C 6 H 5 ) 4 , LiCH 3 SO 3 , LiCF 3 SO 3 , LiAlCl 4 , Li 2 SiF 6 , LiCl, or LiBr.
- any one or more of LiPF 6 , LiBF 4 , LiClO 4 and LiAsF 6 are preferable, LiPF 6 or LiBF 4 is preferable, and LiPF 6 is more preferable. This is because the internal resistance is reduced, so that more excellent characteristics can be obtained.
- the content of the electrolyte salt is preferably 0.3 mol / kg or more and 3.0 mol / kg or less with respect to the solvent. This is because high ionic conductivity is obtained.
- This secondary battery is manufactured by the following procedure, for example.
- a positive electrode active material and, if necessary, a positive electrode binder and a positive electrode conductive agent are mixed to form a positive electrode mixture, which is then dispersed in an organic solvent or the like and pasted.
- a positive electrode mixture slurry is applied to the positive electrode current collector 21A using a coating device such as a doctor blade or a bar coater, and then dried to form the positive electrode active material layer 21B.
- the positive electrode active material layer 21B is compression-molded using a roll press or the like while being heated as necessary. In this case, compression molding may be repeated a plurality of times.
- the negative electrode active material layer 22B is formed on the negative electrode current collector 22A by the same manufacturing procedure as that of the negative electrode described above.
- the positive electrode lead 24 is attached to the positive electrode current collector 21A and the negative electrode lead 25 is attached to the negative electrode current collector 22A by using a welding method or the like. Then, after laminating the positive electrode 21 and the negative electrode 22 via the separator 23, they are wound in the longitudinal direction. Finally, the wound body is molded so as to have a flat shape.
- the battery element 20 When assembling the secondary battery, first, the battery element 20 is accommodated in the battery can 11, and then the insulating plate 12 is placed on the battery element 20. Subsequently, the positive electrode lead 24 is attached to the positive electrode pin 15 and the negative electrode lead 25 is attached to the battery can 11 using a welding method or the like. In this case, the battery lid 13 is fixed to the open end of the battery can 11 using a laser welding method or the like. Finally, after injecting the electrolyte into the battery can 11 from the injection hole 19 and impregnating the separator 23, the injection hole 19 is closed with a sealing member 19A.
- Cylindrical type> 10 and 11 show a cross-sectional configuration of the cylindrical secondary battery.
- a part of the spirally wound electrode body 40 shown in FIG. 10 is enlarged.
- the constituent elements of the already-described prismatic secondary battery are referred to as needed.
- the cylindrical secondary battery mainly includes a wound electrode body 40 and a pair of insulating plates 32 and 33 in a substantially hollow cylindrical battery can 31.
- the wound electrode body 40 is a wound laminated body in which a positive electrode 41 and a negative electrode 42 are laminated and wound via a separator 43.
- the battery can 31 has a hollow structure in which one end is closed and the other end is opened.
- the battery can 31 is made of the same material as the battery can 11.
- the pair of insulating plates 32 and 33 are disposed so as to sandwich the wound electrode body 40 from above and below and to extend perpendicularly to the wound peripheral surface.
- a battery lid 34, a safety valve mechanism 35, and a heat sensitive resistance element (PTC element) 36 are caulked through a gasket 37 at the open end of the battery can 31, and the battery can 31 is sealed.
- the battery lid 34 is formed of the same material as the battery can 31, for example.
- the safety valve mechanism 35 and the thermal resistance element 36 are provided inside the battery lid 34, and the safety valve mechanism 35 is electrically connected to the battery lid 34 via the thermal resistance element 36.
- the disk plate 35A is reversed and the electric power between the battery lid 34 and the wound electrode body 40 is reversed. Connection is cut off.
- the heat-sensitive resistance element 36 prevents abnormal heat generation caused by a large current by increasing resistance in response to a temperature rise.
- the gasket 37 is made of, for example, an insulating material, and asphalt may be applied to the surface thereof.
- a center pin 44 may be inserted in the center of the wound electrode body 40.
- a positive electrode lead 45 formed of a conductive material such as Al is connected to the positive electrode 41, and a negative electrode lead 46 formed of a conductive material such as Ni is connected to the negative electrode 42.
- the positive electrode lead 45 is welded to the safety valve mechanism 35 and is electrically connected to the battery lid 34.
- the negative electrode lead 46 is welded to the battery can 31.
- the positive electrode 41 has, for example, a positive electrode active material layer 41B on both surfaces of the positive electrode current collector 41A.
- the negative electrode 42 has the same configuration as the negative electrode described above, and includes, for example, a negative electrode active material layer 42B on both surfaces of the negative electrode current collector 42A.
- the configurations of the positive electrode current collector 41A, the positive electrode active material layer 41B, the negative electrode current collector 42A, the negative electrode active material layer 42B, and the separator 43 are the positive electrode current collector 21A, the positive electrode active material layer 21B, the negative electrode current collector 22A, and the negative electrode, respectively.
- the configurations of the active material layer 22B and the separator 23 are the same.
- the composition of the electrolytic solution impregnated in the separator 43 is the same as the composition of the electrolytic solution in the square secondary battery.
- This cylindrical secondary battery is manufactured, for example, by the following procedure.
- the positive electrode active material layer 41B is formed on both surfaces of the positive electrode current collector 41A to produce the positive electrode 41 by the same production procedure as that of the positive electrode 21 and the negative electrode 22, and the negative electrode is formed on both surfaces of the negative electrode current collector 42A.
- the active material layer 42B is formed to produce the negative electrode 42.
- the positive electrode lead 45 is attached to the positive electrode 41 and the negative electrode lead 46 is attached to the negative electrode 42.
- the positive electrode 41 and the negative electrode 42 are stacked and wound through the separator 43 to produce the wound electrode body 40, and then the center pin 44 is inserted into the winding center.
- the wound electrode body 40 is accommodated in the battery can 31 while being sandwiched between the pair of insulating plates 32 and 33.
- the positive electrode lead 45 is attached to the safety valve mechanism 35 using a welding method or the like, and the tip of the negative electrode lead 46 is attached to the battery can 31.
- an electrolytic solution is injected into the battery can 31 and impregnated in the separator 43.
- the battery lid 34, the safety valve mechanism 35, and the heat sensitive resistance element 36 are crimped via the gasket 37.
- FIG. 12 shows an exploded perspective configuration of a laminated film type secondary battery
- FIG. 13 is an enlarged cross section taken along line XIII-XIII of the spirally wound electrode body 50 shown in FIG.
- the laminated film type secondary battery is mainly one in which a wound electrode body 50 is housed inside a film-shaped exterior member 60.
- the wound electrode body 50 is a wound laminated body in which a positive electrode 53 and a negative electrode 54 are laminated and wound via a separator 55 and an electrolyte layer 56.
- a positive electrode lead 51 is attached to the positive electrode 53, and a negative electrode lead 52 is attached to the negative electrode 54.
- the outermost peripheral portion of the wound electrode body 50 is protected by a protective tape 57.
- the positive electrode lead 51 and the negative electrode lead 52 are led out in the same direction from the inside of the exterior member 60 to the outside, for example.
- the positive electrode lead 51 is formed of, for example, a conductive material such as Al
- the negative electrode lead 52 is formed of, for example, a conductive material such as Cu, Ni, or stainless steel. These materials have, for example, a thin plate shape or a mesh shape.
- the exterior member 60 is, for example, a laminate film in which a fusion layer, a metal layer, and a surface protective layer are laminated in this order.
- the outer peripheral edge portions of the fusion layers of the two films are bonded together by an adhesive or the like so that the fusion layer faces the wound electrode body 50.
- the fusing layer is, for example, a film of polyethylene or polypropylene.
- the metal layer is, for example, an Al foil.
- the surface protective layer is, for example, a film such as nylon or polyethylene terephthalate.
- the exterior member 60 an aluminum laminated film in which a polyethylene film, an aluminum foil, and a nylon film are laminated in this order is preferable.
- the exterior member 60 may be a laminate film having another laminated structure, a polymer film such as polypropylene, or a metal film.
- An adhesion film 61 is inserted between the exterior member 60 and the positive electrode lead 51 and the negative electrode lead 52 to prevent intrusion of outside air.
- the adhesion film 61 is formed of a material having adhesion to the positive electrode lead 51 and the negative electrode lead 52.
- a material is, for example, a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, or modified polypropylene.
- the positive electrode 53 has, for example, a positive electrode active material layer 53B on both surfaces of the positive electrode current collector 53A.
- the negative electrode 54 has the same configuration as the above-described negative electrode, and includes, for example, a negative electrode active material layer 54B on both surfaces of the negative electrode current collector 54A.
- the configurations of the positive electrode current collector 53A, the positive electrode active material layer 53B, the negative electrode current collector 54A, and the negative electrode active material layer 54B are respectively the positive electrode current collector 21A, the positive electrode active material layer 21B, the negative electrode current collector 22A, and the negative electrode active material layer.
- the configuration is the same as 22B.
- the configuration of the separator 55 is the same as the configuration of the separator 23.
- the electrolyte layer 56 is one in which an electrolytic solution is held by a polymer compound, and may contain other materials such as additives as necessary.
- the electrolyte layer 56 is a so-called gel electrolyte.
- a gel electrolyte is preferable because high ion conductivity (for example, 1 mS / cm or more at room temperature) is obtained and leakage of the electrolyte is prevented.
- polymer compound examples include polyacrylonitrile, polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, polyethylene oxide, polypropylene oxide, polyphosphazene, polysiloxane, polyvinyl fluoride, polyvinyl acetate, polyvinyl alcohol, polymethacryl. Contains one or more of methyl acid, polyacrylic acid, polymethacrylic acid, styrene-butadiene rubber, nitrile-butadiene rubber, polystyrene, polycarbonate, or a copolymer of vinylidene fluoride and hexafluoropyrene It is out. It is. Among these, polyvinylidene fluoride or a copolymer of vinylidene fluoride and hexafluoropyrene is preferable. This is because it is electrochemically stable.
- the composition of the electrolytic solution is, for example, the same as the composition of the electrolytic solution in a square secondary battery.
- the solvent of the electrolytic solution is a wide concept including not only a liquid solvent but also a material having ion conductivity capable of dissociating the electrolyte salt. For this reason, when using the high molecular compound which has ion conductivity, the high molecular compound is also contained in a solvent.
- electrolytic solution may be used instead of the gel electrolyte layer 56.
- the separator 55 is impregnated with the electrolytic solution.
- the laminate film type secondary battery provided with the gel electrolyte layer 56 is manufactured, for example, by the following three types of procedures.
- the positive electrode 53 and the negative electrode 54 are manufactured by the same manufacturing procedure as that of the positive electrode 21 and the negative electrode 22.
- the positive electrode active material layer 53B is formed on both surfaces of the positive electrode current collector 53A to produce the positive electrode 53
- the negative electrode active material layer 54B is formed on both surfaces of the negative electrode current collector 54A to produce the negative electrode 54.
- the precursor solution is applied to the positive electrode 53 and the negative electrode 54 to form a gel electrolyte layer 56.
- the positive electrode lead 51 is attached to the positive electrode current collector 53A, and the negative electrode lead 52 is attached to the negative electrode current collector 54A.
- the positive electrode 53 and the negative electrode 54 on which the electrolyte layer 56 is formed are stacked and wound via a separator 55 to produce a wound electrode body 50, and then a protective tape 57 is bonded to the outermost periphery.
- the outer peripheral edges of the exterior member 60 are bonded to each other by using a heat fusion method or the like, and the exterior member 60
- the wound electrode body 50 is encapsulated.
- the adhesion film 61 is inserted between the positive electrode lead 51 and the negative electrode lead 52 and the exterior member 60.
- the positive electrode lead 51 is attached to the positive electrode 53 and the negative electrode lead 52 is attached to the negative electrode 54.
- the positive electrode 53 and the negative electrode 54 are stacked and wound through the separator 55 to produce a wound body that is a precursor of the wound electrode body 50, and then a protective tape 57 is bonded to the outermost peripheral portion thereof.
- the remaining outer peripheral edge portion excluding the outer peripheral edge portion on one side is adhered by using a heat fusion method or the like, and the bag A wound body is accommodated in the interior of the outer package member 60.
- an electrolyte composition containing an electrolytic solution, a monomer that is a raw material of the polymer compound, a polymerization initiator, and other materials such as a polymerization inhibitor as necessary is prepared to form a bag-shaped exterior member.
- the opening of the exterior member 60 is sealed using a heat fusion method or the like.
- the monomer is thermally polymerized to obtain a polymer compound, and the gel electrolyte layer 56 is formed.
- a wound body is prepared in the interior of the bag-shaped exterior member 60 in the same manner as in the second procedure described above except that the separator 55 coated with the polymer compound on both sides is used.
- the polymer compound applied to the separator 55 is, for example, a polymer (such as a homopolymer, a copolymer, or a multi-component copolymer) containing vinylidene fluoride as a component.
- a binary copolymer comprising polyvinylidene fluoride, vinylidene fluoride and hexafluoropropylene as components, or a ternary copolymer comprising vinylidene fluoride, hexafluoropropylene and chlorotrifluoroethylene as components.
- Etc. In addition to the polymer containing vinylidene fluoride as a component, one or more other polymer compounds may be used. Subsequently, after the electrolytic solution is prepared and injected into the exterior member 60, the opening of the exterior member 60 is sealed using a thermal fusion method or the like.
- the exterior member 60 is heated while applying a load, and the separator 55 is brought into close contact with the positive electrode 53 and the negative electrode 54 through the polymer compound.
- the electrolytic solution is impregnated into the polymer compound, the polymer compound is gelled to form the electrolyte layer 56.
- the secondary battery can be used as long as it is a machine, device, instrument, device or system (an assembly of multiple devices) that can be used as a power source for driving or a power storage source for power storage.
- a secondary battery may be a main power source (a power source used preferentially) or an auxiliary power source (a power source used in place of or switched from the main power source).
- the type of the main power source in the latter case is not limited to the secondary battery.
- Examples of uses of the secondary battery include the following uses. It is a portable electronic device such as a video camera, a digital still camera, a mobile phone, a notebook computer, a cordless phone, a headphone stereo, a portable radio, a portable TV, or a portable information terminal. However, the use of the electronic device is not limited to portable use. It is a portable living device such as an electric shaver. A storage device such as a backup power supply or a memory card. An electric tool such as an electric drill or an electric saw. A battery pack used as a power source for a notebook computer or the like. Medical electronic devices such as pacemakers or hearing aids. An electric vehicle such as an electric vehicle (including a hybrid vehicle). It is an electric power storage system such as a home battery system that stores electric power in case of an emergency. Of course, applications other than those described above may be used.
- a portable electronic device such as a video camera, a digital still camera, a mobile phone, a notebook computer, a cordless phone, a headphone stereo
- the battery pack is a power source using a secondary battery, and is a so-called assembled battery.
- the electric vehicle is a vehicle that operates (runs) using a secondary battery as a driving power source, and may be an automobile (such as a hybrid automobile) that includes a drive source other than the secondary battery as described above.
- the power storage system is a system that uses a secondary battery as a power storage source.
- An electric power tool is a tool in which a movable part (for example, a drill etc.) moves, using a secondary battery as a driving power source.
- An electronic device is a device that exhibits various functions using a secondary battery as a driving power source.
- FIG. 14 shows a block configuration of the battery pack.
- the battery pack includes a control unit 61, a power source 62, a switch unit 63, a current measuring unit 64, a temperature, and the like inside a housing 60 formed of a plastic material or the like.
- a detection unit 65, a voltage detection unit 66, a switch control unit 67, a memory 68, a temperature detection element 69, a current detection resistor 70, a positive electrode terminal 71, and a negative electrode terminal 72 are provided.
- the control unit 61 controls the operation of the entire battery pack (including the usage state of the power supply 62), and includes, for example, a central processing unit (CPU).
- the power source 62 includes one or more secondary batteries (not shown).
- the power source 62 is, for example, an assembled battery including two or more secondary batteries, and the connection form thereof may be in series, in parallel, or a mixture of both.
- the power source 62 includes six secondary batteries connected in two parallel three series.
- the switch unit 63 switches the usage state of the power source 62 (whether or not the power source 62 can be connected to an external device) according to an instruction from the control unit 61.
- the switch unit 63 includes, for example, a charge control switch, a discharge control switch, a charging diode, a discharging diode (all not shown), and the like.
- the charge control switch and the discharge control switch are semiconductor switches such as a field effect transistor (MOSFET) using a metal oxide semiconductor, for example.
- the current measurement unit 64 measures current using the current detection resistor 70 and outputs the measurement result to the control unit 61.
- the temperature detection unit 65 measures the temperature using the temperature detection element 69 and outputs the measurement result to the control unit 61. This temperature measurement result is used, for example, when the control unit 61 performs charge / discharge control during abnormal heat generation, or when the control unit 61 performs correction processing when calculating the remaining capacity.
- the voltage detector 66 measures the voltage of the secondary battery in the power source 62, converts the measured voltage analog / digital conversion (A / D), and supplies the converted voltage to the controller 61.
- the switch control unit 67 controls the operation of the switch unit 63 in accordance with signals input from the current measurement unit 66 and the voltage measurement unit 66.
- the switch control unit 67 disconnects the switch unit 67 (charge control switch) and controls the charging current not to flow through the current path of the power source 62. It is like that. As a result, the power source 62 can only discharge through the discharging diode.
- the switch control unit 67 is configured to cut off the charging current when a large current flows during charging, for example.
- the switch control unit 67 controls the switch unit 67 (discharge control switch) to be disconnected so that the discharge current does not flow in the current path of the power source 62 when the battery voltage reaches the overdischarge detection voltage, for example. It is supposed to be. As a result, the power source 62 can only be charged via the charging diode.
- the switch control unit 67 is configured to cut off the discharge current when a large current flows during discharging.
- the overcharge detection voltage is 4.20V ⁇ 0.05V
- the overdischarge detection voltage is 2.4V ⁇ 0.1V.
- the memory 68 is, for example, an EEPROM which is a nonvolatile memory.
- the memory 68 stores, for example, numerical values calculated by the control unit 61 and information (for example, internal resistance in an initial state) of the secondary battery measured in the manufacturing process stage. If the full charge capacity of the secondary battery is stored in the memory 68, the control unit 10 can grasp information such as the remaining capacity.
- the temperature detection element 69 measures the temperature of the power source 62 and outputs the measurement result to the control unit 61, and is, for example, a thermistor.
- the positive electrode terminal 71 and the negative electrode terminal 72 are connected to an external device (for example, a notebook personal computer) operated using a battery pack or an external device (for example, a charger) used to charge the battery pack. Terminal. Charging / discharging of the power source 62 is performed via the positive terminal 71 and the negative terminal 72.
- an external device for example, a notebook personal computer
- an external device for example, a charger
- FIG. 15 illustrates a block configuration of a hybrid vehicle that is an example of an electric vehicle.
- the electric vehicle includes a control unit 74, an engine 75, a power source 76, a drive motor 77, and a differential device 78 in a metal housing 73. , A generator 79, a transmission 80 and a clutch 81, inverters 82 and 83, and various sensors 84.
- the electric vehicle includes, for example, a front wheel drive shaft 85 and a front wheel 86 connected to the differential device 78 and the transmission 80, and a rear wheel drive shaft 87 and a rear wheel 88.
- the engine 75 is a main power source, such as a gasoline engine.
- the driving force (rotational force) of the engine 75 is transmitted to the front wheels 86 or the rear wheels 88 via, for example, a differential device 78 that is a driving unit, a transmission 80, and a clutch 81.
- the rotational force of the engine 75 is also transmitted to the generator 79.
- the generator 79 generates AC power by the rotational force, and the AC power is converted into DC power via the inverter 83 and stored in the power source 76. Is done.
- the motor 77 serving as a conversion unit when used as a power source, the power (DC power) supplied from the power source 76 is converted into AC power via the inverter 82, and the motor 77 is driven by the AC power.
- the driving force (rotational force) converted from electric power by the motor 77 is transmitted to the front wheels 86 or the rear wheels 88 via, for example, a differential device 78, a transmission 80, and a clutch 81, which are driving units.
- the resistance force at the time of deceleration may be transmitted as a rotational force to the motor 77, and the motor 77 may generate AC power by the rotational force.
- This AC power is preferably converted into DC power via the inverter 82, and the DC regenerative power is preferably stored in the power source 76.
- the control unit 74 controls the operation of the entire electric vehicle and includes, for example, a CPU.
- the power source 76 includes one or more secondary batteries (not shown).
- the power source 76 may be connected to an external power source and can store power by receiving power supply from the external power source.
- the various sensors 84 are used, for example, to control the rotational speed of the engine 75 or to control the opening (throttle opening) of a throttle valve (not shown).
- the various sensors 84 include, for example, a speed sensor, an acceleration sensor, an engine speed sensor, and the like.
- the hybrid vehicle has been described as the electric vehicle.
- the electric vehicle may be a vehicle (electric vehicle) that operates using only the power source 76 and the motor 77 without using the engine 75.
- FIG. 16 shows a block configuration of the power storage system.
- the power storage system includes a control unit 90, a power source 91, a smart meter 92, and a power hub 93 inside a house 89 such as a general house or a commercial building. Yes.
- the power source 91 is connected to, for example, an electric device 94 installed inside the house 89 and can be connected to an electric vehicle 96 stopped outside the house 89.
- the power source 91 is connected to, for example, a private generator 95 installed in a house 89 via a power hub 93 and can be connected to an external centralized power system 97 via the smart meter 92 and the power hub 93. It has become.
- the electric device 94 includes one or more home appliances such as a refrigerator, an air conditioner, a television, or a water heater.
- the private power generator 95 is, for example, one type or two or more types such as a solar power generator or a wind power generator.
- the electric vehicle 96 is, for example, one type or two or more types such as an electric vehicle, an electric motorcycle, or a hybrid vehicle.
- the centralized power system 97 is, for example, one type or two or more types such as a thermal power plant, a nuclear power plant, a hydroelectric power plant, or a wind power plant.
- the control unit 90 controls the operation of the entire power storage system (including the usage state of the power supply 91), and includes, for example, a CPU.
- the power source 91 includes one or more secondary batteries (not shown).
- the smart meter 92 is, for example, a network-compatible power meter installed in a house 89 on the power demand side, and can communicate with the power supply side. Accordingly, for example, the smart meter 92 controls the balance between supply and demand in the house 89 while communicating with the outside as necessary, thereby enabling efficient and stable energy supply.
- the power storage system for example, power is accumulated in the power source 91 from the centralized power system 97 that is an external power source via the smart meter 92 and the power hub 93, and the power hub 93 is connected from the solar power generator 95 that is an independent power source. Power is accumulated in the power source 91 through the power source 91.
- the electric power stored in the power source 91 is supplied to the electric device 94 or the electric vehicle 96 as required in accordance with an instruction from the control unit 91, so that the electric device 94 can be operated and the electric vehicle 96. Can be charged.
- the power storage system is a system that makes it possible to store and supply power in the house 89 using the power source 91.
- the power stored in the power supply 91 can be used arbitrarily. For this reason, for example, power is stored in the power source 91 from the centralized power system 97 at midnight when the amount of electricity used is low, and the power stored in the power source 91 is used during the day when the amount of electricity used is high. it can.
- the power storage system described above may be installed for each house (one household), or may be installed for each of a plurality of houses (multiple households).
- FIG. 17 shows a block configuration of the electric power tool.
- the electric power tool is an electric drill, and includes a control unit 99 and a power source 100 inside a tool main body 98 formed of a plastic material or the like.
- a drill portion 101 which is a movable portion is attached to the tool body 98 so as to be operable (rotatable).
- the control unit 99 controls the operation of the entire power tool (including the usage state of the power supply 100), and includes, for example, a CPU.
- the power supply 100 includes one or more secondary batteries (not shown). This controlled object 99 is moved by supplying electric power from the power supply 100 to the drill unit 101 as necessary in accordance with operation of an operation switch (not shown).
- Example 1-1 to 1-21 The laminate film type secondary battery shown in FIGS. 12 and 13 was produced by the following procedure.
- the positive electrode 53 In producing the positive electrode 53, first, 91 parts by mass of a positive electrode active material (LiCoO 2 ), 6 parts by mass of a positive electrode conductive agent (graphite), 3 parts by mass of a positive electrode binder (polyvinylidene fluoride: PVDF), Were mixed to obtain a positive electrode mixture. Subsequently, the positive electrode mixture was dispersed in an organic solvent (N-methyl-2-pyrrolidone: NMP) to obtain a paste-like positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry was applied to both surfaces of the positive electrode current collector 53A (12 ⁇ m thick strip-like Al foil) using a coating apparatus, and then dried to form the positive electrode active material layer 53B. Finally, the positive electrode active material layer 53B was compression molded using a roll press. In this case, the thickness of the positive electrode active material layer 53B was adjusted so that Li metal did not deposit on the negative electrode 54 during full charge.
- a positive electrode active material LiCo
- the composition (atomic ratio x) was controlled by adjusting the amount of O 2 introduced during the melting and solidification of the raw material (Si).
- a non-crystalline covering portion (SiO y ) was formed on the surface of the core portion using a powder vapor deposition method.
- the composition (atomic ratio y) was controlled by adjusting the amount of O 2 or H 2 introduced during deposition of the raw material (Si).
- the layer structure of the coating part was made multilayer by repeating the deposition process from multiple directions while rotating the core part using a shutter mechanism.
- a carbon-containing material (C) was formed in the voids of the covering portion using a thermal decomposition CVD method (the carbon source gas was methane gas).
- the configurations of the core portion, the covering portion, and the carbon-containing material are as shown in Table 1.
- the negative electrode active material and the negative electrode binder precursor were mixed at a dry weight ratio of 90:10, and then diluted with NMP to obtain a paste-like negative electrode mixture slurry.
- NMP N-dimethylacetamide
- the negative electrode binder precursor polyamic acid containing NMP and N, N-dimethylacetamide (DMAC) was used.
- the negative electrode mixture slurry was applied to both surfaces of the negative electrode current collector 54A (15 ⁇ m-thick rolled Cu foil) using a coating apparatus, and then dried. Finally, in order to enhance the binding property, the coating film was hot-pressed and then fired in a vacuum atmosphere (400 ° C. ⁇ 1 hour).
- the negative electrode binder polyamideimide
- the negative electrode active material layer 54B containing a negative electrode active material and a negative electrode binder was formed. Note that the thickness of the negative electrode active material layer 54B was adjusted so that the negative electrode utilization rate was 65%.
- the electrolyte salt (LiPF 6 ) was dissolved in a solvent (ethylene carbonate (EC) and diethyl carbonate (DEC)).
- a solvent ethylene carbonate (EC) and diethyl carbonate (DEC)
- the positive electrode lead 51 made of Al was welded to one end of the positive electrode current collector 53A, and the negative electrode lead 52 made of Ni was welded to one end of the negative electrode current collector 54A.
- the positive electrode 53, the separator 55, the negative electrode 54, and the separator 55 are laminated in this order and then wound in the longitudinal direction to form a wound body that is a precursor of the wound electrode body 50.
- the winding end portion was fixed with a protective tape 57 (adhesive tape).
- a laminated film (thickness: 20 ⁇ m) in which a film mainly composed of porous polyethylene was sandwiched between films mainly composed of porous polypropylene.
- the outer peripheral edge portions except for one side were heat-sealed, and the wound body was housed inside the bag-shaped exterior member 60.
- an aluminum laminate film in which a nylon film (30 ⁇ m thickness), an Al foil (40 ⁇ m thickness), and an unstretched polypropylene film (30 ⁇ m thickness) were laminated from the outside was used as the exterior member 60.
- an electrolytic solution was injected from the opening of the exterior member 60 and impregnated in the separator 55 to produce the wound electrode body 50. Finally, the opening of the exterior member 60 was heat-sealed in a vacuum atmosphere.
- the atomic ratio x of the core portion satisfies 0 ⁇ x ⁇ 0.5 and the atomic ratio y of the covering portion is 0.5 ⁇ y ⁇ 1.
- 8 When 8 was satisfied, higher initial efficiency and capacity maintenance ratio were obtained.
- Example 2 (Experimental examples 2-1 to 2-10) As shown in Table 2, a secondary battery was fabricated in the same manner as in Experimental Example 1-5, except that the crystallinity (specific IG / ID) of the carbon-containing material was changed, and various characteristics were examined. In this case, the ratio IG / ID was adjusted by changing the pressure, decomposition temperature, and gas type during the formation of the carbon-containing material.
- the void diameter was 500 nm or less, and further 50 nm or less, high initial efficiency and capacity retention were obtained, and high battery capacity was also obtained.
- Example 4 As shown in Table 4, a secondary battery was fabricated in the same manner as in Experimental Example 1-5, except that the median diameter (D50) of the core portion was changed, and various characteristics were examined. In this case, the median diameter (D50) of the core part was adjusted using raw materials (Si) having different median diameters (D50).
- Example 5 As shown in Table 5, a secondary battery was fabricated in the same manner as in Experimental Example 1-5, except that the average coverage and average thickness of the coating portion were changed, and various characteristics were examined. In this case, when forming the covering portion, the average coverage was adjusted by changing the input power and the deposition time, and the average thickness was adjusted by changing the deposition rate and the deposition time.
- Example 6 As shown in Table 6, a secondary battery was prepared in the same manner as in Experimental Example 1-5, except that the crystallinity of the covering portion was changed, and various characteristics were examined. In this case, the depositing while heating the SiO y to form a low-crystalline coating section in an atmosphere of Ar gas. The temperature and time during the heating were adjusted to adjust the physical properties (average area occupancy, average particle size, and size relationship) of the coating as shown in Table 6. This “magnitude relationship” is a size relationship between the average area occupancy ratio and the average particle diameter in the inner part and the outer part when the coating portion is divided into two equal parts in the thickness direction.
- the average area occupancy was 35% or less
- the average particle size was 50 nm or less
- the average area occupancy and the average particle size were inside ⁇ outside, a higher capacity retention rate was obtained.
- Example 7 As shown in Table 7, a secondary battery was fabricated in the same manner as in Experimental Example 1-5, except that a carbon-containing layer was formed on the surface of the negative electrode active material, and various characteristics were examined.
- the procedure for forming the carbon-containing layer is the same as the procedure for forming the carbon-containing material. In this case, by adjusting the pressure during pyrolysis as necessary, a part of the carbon-containing layer is embedded in the voids of the covering portion instead of the carbon-containing material, and the voids are part of the carbon-containing layer. Sealed with.
- the initial efficiency and the capacity maintenance rate were further increased.
- the average thickness was 500 nm or less and the average coverage was 30% to 100%, higher initial efficiency and capacity retention were obtained, and higher battery capacity was also obtained.
- Example 8-1 to 8-17, 9-1 to 9-5) As shown in Tables 8 and 9, a secondary battery was fabricated in the same manner as in Experimental Example 1-5, except that a metal element was contained in the core part and the covering part, and various characteristics were examined. In this case, co-evaporation was performed using SiO x powder and metal powder as raw materials.
- the initial efficiency and the capacity maintenance rate were further increased.
- Fe when the metal element was contained in the core part and the covering part, the initial efficiency and the capacity maintenance rate were further increased.
- a high cycle maintenance ratio and initial efficiency were obtained when the Fe content was 0.01 wt% to 7.5 wt%.
- Example 10-1 to 10-3 As shown in Table 10, a secondary battery was fabricated in the same manner as in Experimental Example 1-5, except that C and S were contained in the anode current collector 54A, and various characteristics were examined. In this case, a rolled Cu foil containing C and S was used as the negative electrode current collector 54A.
- Example 11-1 to 11-9 As shown in Table 11, a secondary battery was prepared in the same manner as in Experimental Example 1-5, except that the type of the negative electrode binder was changed, and various characteristics were examined.
- a negative electrode binder polyimide (PI), polyvinylidene fluoride (PVDF), polyamide (PA), polyacrylic acid (PAA), polyacrylic acid lithium (PAAL), polyimide carbide (carbonized PI), Polyethylene (PE), polymaleic acid (PMA), or aramid (AR) was used.
- PAA, PAAL, etc. while preparing the negative mix slurry using the 17 volume% aqueous solution in which they were melt
- Example 12 As shown in Table 12, a secondary battery was prepared in the same manner as in Experimental Example 1-5, except that the type of the positive electrode active material was changed, and various characteristics were examined.
- the capacity of the negative electrode includes a capacity due to insertion and extraction of lithium ions and a capacity due to precipitation and dissolution of lithium metal, and a secondary capacity in which the battery capacity is represented by the sum of these capacities.
- a negative electrode material capable of occluding and releasing lithium ions is used, and the chargeable capacity of the negative electrode material is set to be smaller than the discharge capacity of the positive electrode.
- the secondary battery of the present technology can be similarly applied to a case where it has another battery structure such as a coin type or a button type, and a case where the battery element has another structure such as a laminated structure.
- the electrode reactant may be another group 1 element such as Na or K, a group 2 element such as Mg or Ca, or another light metal such as Al. Since the effect of the present technology should be obtained without depending on the type of the electrode reactant, the same effect can be obtained even if the type of the electrode reactant is changed.
- the appropriate ranges derived from the results of the examples are described with respect to the atomic ratios x and y of the core portion and the covering portion.
- the explanation does not completely deny the possibility that the atomic ratio x, y is outside the above range. That is, the appropriate range described above is a particularly preferable range for obtaining the effects of the present technology. Therefore, the atomic ratios x and y may slightly deviate from the above ranges as long as the effects of the present technology can be obtained. .
- a positive electrode, a negative electrode containing an active material, and an electrolyte solution The active material includes a core part capable of occluding and releasing lithium ions, and a low crystalline or non-crystalline covering part provided on at least a part of the surface of the core part,
- the core portion includes Si and O as constituent elements, and an atomic ratio x (O / Si) of O to Si satisfies 0 ⁇ x ⁇ 0.5
- the covering portion includes Si and O as constituent elements, and an atomic ratio y (O / Si) of O to Si satisfies 0.5 ⁇ y ⁇ 1.8,
- the covering portion has a void, and a carbon-containing material is provided in at least a part of the void.
- the ratio IG / ID between the G band peak intensity IG and the D band peak intensity ID of the carbon-containing material measured by the Raman spectrum method is 0.3 to 3.
- (3) The maximum peak void diameter in the void distribution of the covering portion measured by a nitrogen adsorption method and a mercury intrusion method is 500 nm or less.
- (4) The covering portion is multilayer.
- a carbon-containing layer is provided on at least a part of the surface of the active material; The average thickness of the carbon-containing layer is 500 nm or less, The average coverage of the carbon-containing layer with respect to the active material is 30% or more.
- the median diameter (D50) of the core is 0.1 ⁇ m to 20 ⁇ m
- the covering part has an average thickness of 1 nm to 3000 nm
- the average coverage of the covering portion with respect to the core portion is 30% or more.
- the crystallinity of the covering portion is lower than the crystallinity of the core portion,
- the covering portion has a low crystallinity including a non-crystalline region and a crystal region (crystal grains), and the crystal grains are scattered in the non-crystalline region.
- the average area occupation ratio of the crystal grains due to the (111) plane and the (220) plane of Si is 35% or less, and the average grain size of the crystal grains is 50 nm or less,
- the covering portion is divided into two equal parts in the thickness direction, the average area occupancy and the average grain size in the inner part of the crystal grains due to the (111) face and the (220) face of Si are the average area in the outer part. Equal to or greater than the occupancy and average particle size,
- the covering is non-crystalline, The secondary battery according to any one of (1) to (7) above.
- the core portion contains Fe as a constituent element, and the ratio of Fe to Si and O (Fe / (Si + O)) is 0.01 wt% to 7.5 wt%.
- the core portion includes at least one of Fe, Al, Ca, Mn, Cr, Mg and Ni as a constituent element,
- the covering portion includes at least one of Fe, Al, and Ca as a constituent element.
- the negative electrode has an active material layer on a current collector, and the active material layer includes the active material,
- the current collector contains C and S as constituent elements and their content is 100 ppm or less.
- the active material includes a core part capable of occluding and releasing lithium ions, and a low crystalline or non-crystalline covering part provided on at least a part of the surface of the core part,
- the core portion includes Si and O as constituent elements, and an atomic ratio x (O / Si) of O to Si satisfies 0 ⁇ x ⁇ 0.5
- the covering portion includes Si and O as constituent elements, and an atomic ratio y (O / Si) of O to Si satisfies 0.5 ⁇ y ⁇ 1.8
- the covering portion has a void, and a carbon-containing material is provided in at least a part of the void. Secondary battery electrode.
- the core portion includes Si and O as constituent elements, and an atomic ratio x (O / Si) of O to Si satisfies 0 ⁇ x ⁇ 0.5
- the covering portion includes Si and O as constituent elements, and an atomic ratio y (O / Si) of O to Si satisfies 0.5 ⁇ y ⁇ 1.8
- the covering portion has a void, and a carbon-containing material is provided in at least a part of the void. Active material for secondary batteries.
- the secondary battery according to any one of (1) to (13) is provided as a power supply source. Electronics.
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Abstract
Description
特許文献2:特開2002-042806号公報
特許文献3:特開2006-164954号公報
特許文献4:特開2006-114454号公報
特許文献5:特開2009-070825号公報
特許文献6:特開2008-282819号公報
特許文献7:国際公開第2007/010922号パンフレット
特許文献8:特開2008-251369号公報
特許文献9:特開2008-177346号公報
特許文献10:特開2007-234255号公報
特許文献11:特開2009-212074号公報
特許文献12:特開2009-205950号公報
特許文献13:特開2009-076373号公報
特許文献14:特許第2997741号明細書
特許文献15:特開2009-164104号公報
特許文献16:特開2006-100244号公報
1.二次電池用活物質
2.二次電池
2-1.角型
2-2.円筒型
2-3.ラミネートフィルム型
3.二次電池の用途
3-1.電池パック
3-2.電動車両
3-3.電力貯蔵システム
3-4.電動工具
図1は、本技術の一実施形態の二次電池用活物質を用いた負極の断面構成を表しており、図2は、本技術の一実施形態の二次電池用活物質である負極活物質の断面構成を表している。図3~図6は、負極活物質の断面構造のHAADF STEM写真(以下、単に「TEM写真」という。)である。
負極は、例えば、図1に示したように、負極集電体1の上に負極活物質層2を有している。この負極活物質層2は、負極集電体1の両面に設けられていてもよいし、片面だけに設けられていてもよい。ただし、負極集電体1はなくてもよい。
負極集電体1は、例えば、電気化学的安定性、電気伝導性および機械的強度に優れた導電性材料により形成されており、その導電性材料は、例えば、Cu、Niまたはステンレスなどの金属材料である。中でも、Liと金属間化合物を形成しないと共に負極活物質層2と合金化する材料が好ましい。
負極活物質層2は、図2に示したように、電極反応物質(リチウムイオン)を吸蔵放出可能である1または2以上の粒子状の負極活物質200を含んでおり、必要に応じて、さらに負極結着剤または負極導電剤などの他の材料を含んでいてもよい。
コア部201は、SiおよびOを構成元素として含んでおり、そのSiに対するOの原子比x(O/Si)は、0≦x<0.5を満たしている。より具体的には、コア部201は、例えば、ケイ素系材料(SiOx :0≦x<0.5)を含んでいる。原子比xが範囲外である場合(x≧0.5)と比較して、充放電時においてコア部201がリチウムイオンを吸蔵放出しやすくなると共に不可逆容量が減少するため、高い電池容量が得られるからである。
被覆部202は、コア部201の表面のうちの少なくとも一部に設けられている。このため、被覆部202は、コア部201の表面の一部だけを被覆していてもよいし、全部を被覆していてもよい。前者の場合には、被覆部202がコア部201の表面において複数箇所に点在していてもよい。
特に、被覆部202は、その内部に1または2以上の空隙を有しており、その空隙のうちの少なくとも一部に、Cを構成元素として含む材料(炭素含有材料)が設けられている。すなわち、炭素含有材料は空隙に挿入されており、その空隙は炭素含有材料により埋められている。上記したコア部201の膨張収縮に追随する被覆部202の膨張収縮性を阻害せずに、負極活物質200の導電性が向上すると共に電解液の分解反応が抑制されるからである。
負極活物質200の表面に炭素含有層が設けられていてもよい。この炭素含有層は、負極活物質200の表面のうちの少なくとも一部に設けられており、コア部201および被覆部202よりも低い電気抵抗を有していることが好ましい。コア部201が電解液とより接触しにくくなるため、その電解液の分解反応が抑制されるからである。また、負極活物質200の電気抵抗がより低下するからである。
この負極は、例えば、以下の手順により製造される。なお、負極集電体1および負極活物質層2の形成材料に関しては既に詳細に説明したので、その説明を省略する。
この負極活物質によれば、負極活物質200がコア部201の表面に低結晶性または非結晶性の被覆部202を有しており、そのコア部201および被覆部20が上記した組成を有している。また、被覆部202の空隙に炭素含有材料が設けられている。これにより、上記したように、コア部201がリチウムイオンを円滑に吸蔵放出しやすくなると共に、そのコア部201が充放電時において破損しにくくなる。また、コア部201の円滑な吸蔵放出を維持したまま、被覆部202の存在に起因して不可逆容量が生じることが抑制される。しかも、負極活物質200の導電性が向上すると共に、高反応性の被覆部202に起因する電解液の分解反応が抑制される。よって、負極活物質または負極を用いた二次電池の性能向上に寄与できる。
次に、上記した二次電池用活物質を用いた二次電池について説明する。
図7および図8は、角型の二次電池の断面構成を表しており、図8では、図7に示したVIII-VIII線に沿った断面を示している。また、図9は、図8に示した正極21および負極22の平面構成を模式的に表している。
角型の二次電池は、主に、電池缶11の内部に電池素子20が収納されたものである。この電池素子20は、セパレータ23を介して正極21と負極22とが積層および巻回された巻回積層体であり、電池缶11の形状に応じて扁平状になっている。
正極21は、例えば、正極集電体21Aの両面に正極活物質層21Bを有している。ただし、正極活物質層21Bは、正極集電体21Aの片面だけに設けられていてもよい。
(M13はCo、Mn、Fe、Al、V、Sn、Mg、Ti、Sr、Ca、Zr、Mo、Tc、Ru、Ta、W、Re、Y、Cu、Zn、Ba、B、Cr、Si、Ga、P、SbおよびNbのうちの少なくとも1種であり、xは0.005<x<0.5を満たす。)
負極22は、上記した負極と同様の構成を有しており、例えば、負極集電体22Aの両面に負極活物質層22Bを有している。負極集電体22Aおよび負極活物質層22Bの構成は、それぞれ負極集電体1および負極活物質層2の構成と同様である。リチウムイオンを吸蔵放出可能である負極材料の充電可能な容量は、正極21の放電容量よりも大きくなっていることが好ましい。充放電時に意図せずにLi金属が析出することを防止するためである。
セパレータ23は、正極21と負極22とを隔離して、両極の接触に起因する電流の短絡を防止しながらリチウムイオンを通過させるものである。このセパレータ23は、例えば、合成樹脂またはセラミックからなる多孔質膜であり、2種類以上の多孔質膜が積層された積層膜でもよい。合成樹脂は、例えば、ポリテトラフルオロエチレン、ポリプロピレンまたはポリエチレンなどである。
セパレータ23には、液状の電解質である電解液が含浸されている。この電解液は、溶媒に電解質塩が溶解されたものであり、必要に応じて添加剤などの他の材料を含んでいてもよい。
この角型の二次電池では、例えば、充電時において、正極21から放出されたリチウムイオンが電解液を介して負極22に吸蔵されると共に、放電時において、負極22から放出されたリチウムイオンが電解液を介して正極21に吸蔵される。
この二次電池は、例えば、以下の手順により製造される。
この角型の二次電池によれば、負極22が上記した負極と同様の構成を有しているので、優れた電池特性を得ることができる。これ以外の効果は、負極と同様である。
図10および図11は、円筒型二次電池の断面構成を表しており、図11では、図10に示した巻回電極体40の一部を拡大している。以下では、既に説明した角型の二次電池の構成要素を随時引用する。
円筒型の二次電池は、主に、ほぼ中空円柱状の電池缶31の内部に巻回電極体40および一対の絶縁板32,33が収納されたものである。この巻回電極体40は、セパレータ43を介して正極41と負極42とが積層および巻回された巻回積層体である。
この円筒型の二次電池では、例えば、充電時において、正極41から放出されたリチウムイオンが電解液を介して負極42に吸蔵されると共に、放電時において、負極42から放出された電解液を介して正極41に吸蔵される。
この円筒型の二次電池は、例えば、以下の手順により製造される。最初に、例えば、正極21および負極22と同様の作製手順により、正極集電体41Aの両面に正極活物質層41Bを形成して正極41を作製すると共に、負極集電体42Aの両面に負極活物質層42Bを形成して負極42を作製する。続いて、溶接法などを用いて、正極41に正極リード45を取り付けると共に、負極42に負極リード46を取り付ける。続いて、セパレータ43を介して正極41と負極42とを積層および巻回させて巻回電極体40を作製したのち、その巻回中心にセンターピン44を挿入する。続いて、一対の絶縁板32,33で挟みながら巻回電極体40を電池缶31の内部に収納する。この場合には、溶接法などを用いて、正極リード45を安全弁機構35に取り付けると共に、負極リード46の先端部を電池缶31に取り付ける。続いて、電池缶31の内部に電解液を注入してセパレータ43に含浸させる。最後に、電池缶31の開口端部に電池蓋34、安全弁機構35および熱感抵抗素子36を取り付けたのち、それらをガスケット37を介してかしめる。
この円筒型の二次電池によれば、負極42が上記した負極と同様の構成を有しているので、角型の二次電池と同様の効果を得ることができる。
図12は、ラミネートフィルム型二次電池の分解斜視構成を表しており、図13は、図12に示した巻回電極体50のXIII-XIII線に沿った断面を拡大している。
ラミネートフィルム型の二次電池は、主に、フィルム状の外装部材60の内部に巻回電極体50が収納されたものである。この巻回電極体50は、セパレータ55および電解質層56を介して正極53と負極54とが積層および巻回された巻回積層体である。正極53には正極リード51が取り付けられていると共に、負極54には負極リード52が取り付けられている。巻回電極体50の最外周部は、保護テープ57により保護されている。
このラミネートフィルム型の二次電池では、例えば、充電時において、正極53から放出されたリチウムイオンが電解質層56を介して負極54に吸蔵される。また、例えば、放電時において、負極54から放出されたリチウムイオンが電解質層56を介して正極53に吸蔵される。
このゲル状の電解質層56を備えたラミネートフィルム型の二次電池は、例えば、以下の3種類の手順により製造される。
このラミネートフィルム型の二次電池では、負極54が上記した負極と同様の構成を有しているので、角型の二次電池と同様の効果を得ることができる。
次に、上記した二次電池の適用例について説明する。
図14は、電池パックのブロック構成を表している。この電池パックは、例えば、図14に示したように、プラスチック材料などにより形成された筐体60の内部に、制御部61と、電源62と、スイッチ部63と、電流測定部64と、温度検出部65と、電圧検出部66と、スイッチ制御部67と、メモリ68と、温度検出素子69と、電流検出抵抗70と、正極端子71および負極端子72とを備えている。
図15は、電動車両の一例であるハイブリッド自動車のブロック構成を表している。この電動車両は、例えば、図15に示したように、金属製の筐体73の内部に、制御部74と、エンジン75と、電源76と、駆動用のモータ77と、差動装置78と、発電機79と、トランスミッション80およびクラッチ81と、インバータ82,83と、各種センサ84とを備えている。この他、電動車両は、例えば、差動装置78およびトランスミッション80に接続された前輪用駆動軸85および前輪86と、後輪用駆動軸87および後輪88とを備えている。
図16は、電力貯蔵システムのブロック構成を表している。この電力貯蔵システムは、例えば、図16に示したように、一般住宅または商業用ビルなどの家屋89の内部に、制御部90と、電源91と、スマートメータ92と、パワーハブ93とを備えている。
図17は、電動工具のブロック構成を表している。この電動工具は、例えば、図17に示したように、電動ドリルであり、プラスチック材料などにより形成された工具本体98の内部に、制御部99と、電源100とを備えている。この工具本体98には、例えば、可動部であるドリル部101が稼働(回転)可能に取り付けられている。
以下の手順により、図12および図13に示したラミネートフィルム型の二次電池を作製した。
表2に示したように、炭素含有材料の結晶性(比IG/ID)を変更したことを除き、実験例1-5と同様の手順により二次電池を作製して諸特性を調べた。この場合には、炭素含有材料の形成時における圧力、分解温度およびガス種を変更して比IG/IDを調整した。
表3に示したように、被覆部の空隙径を変更したことを除き、実験例1-5と同様の手順により二次電池を作製して諸特性を調べた。この場合には、被覆部の形成時において、蒸着流に対するコア部の角度を不連続的に変化させることで空隙径を調整した。
表4に示したように、コア部のメジアン径(D50)を変更したことを除き、実験例1-5と同様の手順により二次電池を作製して諸特性を調べた。この場合には、メジアン径(D50)が異なる原材料(Si)を用いてコア部のメジアン径(D50)を調整した。
表5に示したように、被覆部の平均被覆率および平均厚さを変更したことを除き、実験例1-5と同様の手順により二次電池を作製して諸特性を調べた。この場合には、被覆部を形成する際に、投入電力および堆積時間を変化させて平均被覆率を調整すると共に、堆積速度および堆積時間を変化させて平均厚さを調整した。
表6に示したように、被覆部の結晶性を変更したことを除き、実験例1-5と同様の手順により二次電池を作製して諸特性を調べた。この場合には、Arガスの雰囲気中においてSiOy を加熱しながら堆積させて低結晶性の被覆部を形成した。この加熱時の温度および時間を調整して、表6に示したように被覆部の物性(平均面積占有率、平均粒径および大小関係)を調整した。この「大小関係」とは、被覆部を厚さ方向において二等分したときの内側部分および外側部分における平均面積占有率および平均粒径の大小関係である。
表7に示したように、負極活物質の表面に炭素含有層を形成したことを除き、実験例1-5と同様の手順により二次電池を作製して諸特性を調べた。この炭素含有層の形成手順は、炭素含有材料の形成手順と同様である。この場合には、必要に応じて熱分解時の圧力を調整することで、被覆部の空隙に炭素含有材料の代わりに炭素含有層の一部を埋め込んで、その空隙を炭素含有層の一部で封孔した。
表8および表9に示したように、コア部および被覆部に金属元素を含有させたことを除き、実験例1-5と同様の手順により二次電池を作製して諸特性を調べた。この場合には、原材料としてSiOx 粉および金属粉を用いて共蒸着した。
表10に示したように、負極集電体54AにCおよびSを含有させたことを除き、実験例1-5と同様の手順により二次電池を作製して諸特性を調べた。この場合には、負極集電体54AとしてCおよびSが含有された圧延Cu箔を用いた。
表11に示したように、負極結着剤の種類を変更したことを除き、実験例1-5と同様の手順により二次電池を作製して諸特性を調べた。この場合には、負極結着剤として、ポリイミド(PI)、ポリフッ化ビニリデン(PVDF)、ポリアミド(PA)、ポリアクリル酸(PAA)、ポリアクリル酸リチウム(PAAL)、炭化ポリイミド(炭化PI)、ポリエチレン(PE)、ポリマレイン酸(PMA)、またはアラミド(AR)を用いた。なお、PAAおよびPAALなどを用いる場合には、それらが溶解された17体積%の水溶液を用いて負極合剤スラリーを準備すると共に、熱プレスしてから焼成しないで負極活物質層54Bを形成した。
表12に示したように、正極活物質の種類を変更したことを除き、実験例1-5と同様の手順により二次電池を作製して諸特性を調べた。
(1)
正極と、活物質を含む負極と、電解液とを備え、
前記活物質は、リチウムイオンを吸蔵放出可能であるコア部と、そのコア部の表面のうちの少なくとも一部に設けられた低結晶性または非結晶性の被覆部とを含み、
前記コア部はSiおよびOを構成元素として含み、そのSiに対するOの原子比x(O/Si)は0≦x<0.5を満たし、
前記被覆部はSiおよびOを構成元素として含み、そのSiに対するOの原子比y(O/Si)は0.5≦y≦1.8を満たし、
前記被覆部は空隙を有し、その空隙のうちの少なくとも一部に炭素含有材料が設けられている、
二次電池。
(2)
ラマンスペクトル法により測定される前記炭素含有材料のGバンドピーク強度IGとDバンドピーク強度IDとの比IG/IDは0.3~3である、
上記(1)に記載の二次電池。
(3)
窒素吸着法および水銀圧入法により測定される前記被覆部の空隙分布における最大ピークの空隙径は500nm以下である、
上記(1)または(2)に記載の二次電池。
(4)
前記被覆部は多層である、
上記(1)ないし(3)のいずれかに記載の二次電池。
(5)
前記活物質の表面のうちの少なくとも一部に炭素含有層が設けられており、
前記炭素含有層の平均厚さは500nm以下であり、
前記活物質に対する前記炭素含有層の平均被覆率は30%以上である、
上記(1)ないし(4)のいずれかに記載の二次電池。
(6)
前記コア部のメジアン径(D50)は0.1μm~20μmであり、
前記被覆部の平均厚さは1nm~3000nmであり、
前記コア部に対する前記被覆部の平均被覆率は30%以上である、
上記(1)ないし(5)のいずれかに記載の二次電池。
(7)
前記被覆部の結晶性は前記コア部の結晶性よりも低い、
上記(1)ないし(6)のいずれかに記載の二次電池。
(8)
前記被覆部は非結晶領域および結晶領域(結晶粒)を含む低結晶性であり、その結晶粒は前記非結晶領域の中に点在する、
上記(1)ないし(7)のいずれかに記載の二次電池。
(9)
Siの(111)面および(220)面に起因する前記結晶粒の平均面積占有率は35%以下であり、その結晶粒の平均粒径は50nm以下であり、
前記被覆部を厚さ方向において二等分したとき、Siの(111)面および(220)面に起因する前記結晶粒の内側部分における平均面積占有率および平均粒径は、外側部分における平均面積占有率および平均粒径と同じであるか、それらよりも大きい、
上記(8)に記載の二次電池。
(10)
前記被覆部は非結晶性である、
上記(1)ないし(7)のいずれかに記載の二次電池。
(11)
前記コア部はFeを構成元素として含み、そのSiおよびOに対するFeの割合(Fe/(Si+O))は0.01重量%~7.5重量%である、
上記(1)ないし(10)のいずれかに記載の二次電池。
(12)
前記コア部はFe、Al、Ca、Mn、Cr、MgおよびNiのうちの少なくとも1種を構成元素として含み、
前記被覆部はFe、AlおよびCaのうちの少なくとも1種を構成元素として含む、
上記(1)ないし(10)のいずれかに記載の二次電池。
(13)
前記負極は集電体の上に活物質層を有し、その活物質層は前記活物質を含み、
前記集電体はCおよびSを構成元素として含むと共にそれらの含有量は100ppm以下である、
上記(1)ないし(12)のいずれかに記載の二次電池。
(14)
活物質を含み、
前記活物質は、リチウムイオンを吸蔵放出可能であるコア部と、そのコア部の表面のうちの少なくとも一部に設けられた低結晶性または非結晶性の被覆部とを含み、
前記コア部はSiおよびOを構成元素として含み、そのSiに対するOの原子比x(O/Si)は0≦x<0.5を満たし、
前記被覆部はSiおよびOを構成元素として含み、そのSiに対するOの原子比y(O/Si)は0.5≦y≦1.8を満たし、
前記被覆部は空隙を有し、その空隙のうちの少なくとも一部に炭素含有材料が設けられている、
二次電池用電極。
(15)
リチウムイオンを吸蔵放出可能であるコア部と、そのコア部の表面のうちの少なくとも一部に設けられた低結晶性または非結晶性の被覆部とを含み、
前記コア部はSiおよびOを構成元素として含み、そのSiに対するOの原子比x(O/Si)は0≦x<0.5を満たし、
前記被覆部はSiおよびOを構成元素として含み、そのSiに対するOの原子比y(O/Si)は0.5≦y≦1.8を満たし、
前記被覆部は空隙を有し、その空隙のうちの少なくとも一部に炭素含有材料が設けられている、
二次電池用活物質。
(16)
上記(1)ないし(13)のいずれかに記載の二次電池と、
その二次電池の使用状態を制御する制御部と、
その制御部の指示に応じて前記二次電池の使用状態を切り換えるスイッチ部と
を備えた、電池パック。
(17)
上記(1)ないし(13)のいずれかに記載の二次電池と、
その二次電池から供給された電力を駆動力に変換する変換部と、
その駆動力に応じて駆動する駆動部と、
前記二次電池の使用状態を制御する制御部と
を備えた、電動車両。
(18)
上記(1)ないし(13)のいずれかに記載の二次電池と、
その二次電池から電力を供給される1または2以上の電気機器と、
前記二次電池からの前記電気機器に対する電力供給を制御する制御部と
を備えた、電力貯蔵システム。
(19)
上記(1)ないし(13)のいずれかに記載の二次電池と、
その二次電池から電力を供給される可動部と
を備えた、電動工具。
(20)
上記(1)ないし(13)のいずれかに記載の二次電池を電力供給源として備えた、
電子機器。
Claims (15)
- 正極と、活物質を含む負極と、電解液とを備え、
前記活物質は、リチウムイオンを吸蔵放出可能であるコア部と、そのコア部の表面のうちの少なくとも一部に設けられた低結晶性または非結晶性の被覆部とを含み、
前記コア部はSiおよびOを構成元素として含み、そのSiに対するOの原子比x(O/Si)は0≦x<0.5を満たし、
前記被覆部はSiおよびOを構成元素として含み、そのSiに対するOの原子比y(O/Si)は0.5≦y≦1.8を満たし、
前記被覆部は空隙を有し、その空隙のうちの少なくとも一部に炭素含有材料が設けられている、
二次電池。 - ラマンスペクトル法により測定される前記炭素含有材料のGバンドピーク強度IGとDバンドピーク強度IDとの比IG/IDは0.3~3である、
請求項1記載の二次電池。 - 窒素吸着法および水銀圧入法により測定される前記被覆部の空隙分布における最大ピークの空隙径は500nm以下である、
請求項1記載の二次電池。 - 前記被覆部は多層である、
請求項1記載の二次電池。 - 前記活物質の表面のうちの少なくとも一部に炭素含有層が設けられており、
前記炭素含有層の平均厚さは500nm以下であり、
前記活物質に対する前記炭素含有層の平均被覆率は30%以上である、
請求項1記載の二次電池。 - 前記コア部のメジアン径(D50)は0.1μm~20μmであり、
前記被覆部の平均厚さは1nm~3000nmであり、
前記コア部に対する前記被覆部の平均被覆率は30%以上である、
請求項1記載の二次電池。 - 前記被覆部の結晶性は前記コア部の結晶性よりも低い、
請求項1記載の二次電池。 - 前記被覆部は非結晶領域および結晶領域(結晶粒)を含む低結晶性であり、その結晶粒は前記非結晶領域の中に点在する、
請求項1記載の二次電池。 - Siの(111)面および(220)面に起因する前記結晶粒の平均面積占有率は35%以下であり、その結晶粒の平均粒径は50nm以下であり、
前記被覆部を厚さ方向において二等分したとき、Siの(111)面および(220)面に起因する前記結晶粒の内側部分における平均面積占有率および平均粒径は、外側部分における平均面積占有率および平均粒径と同じであるか、それらよりも大きい、
請求項8記載の二次電池。 - 前記被覆部は非結晶性である、
請求項1記載の二次電池。 - 前記コア部はFeを構成元素として含み、そのSiおよびOに対するFeの割合(Fe/(Si+O))は0.01重量%~7.5重量%である、
請求項1記載の二次電池。 - 前記コア部はFe、Al、Ca、Mn、Cr、MgおよびNiのうちの少なくとも1種を構成元素として含み、
前記被覆部はFe、AlおよびCaのうちの少なくとも1種を構成元素として含む、
請求項1記載の二次電池。 - 前記負極は集電体の上に活物質層を有し、その活物質層は前記活物質を含み、
前記集電体はCおよびSを構成元素として含むと共にそれらの含有量は100ppm以下である、
請求項1記載の二次電池。 - リチウムイオンを吸蔵放出可能であるコア部と、そのコア部の表面のうちの少なくとも一部に設けられた低結晶性または非結晶性の被覆部とを含み、
前記コア部はSiおよびOを構成元素として含み、そのSiに対するOの原子比x(O/Si)は0≦x<0.5を満たし、
前記被覆部はSiおよびOを構成元素として含み、そのSiに対するOの原子比y(O/Si)は0.5≦y≦1.8を満たし、
前記被覆部は空隙を有し、その空隙のうちの少なくとも一部に炭素含有材料が設けられている、
二次電池用活物質。 - 二次電池を電力供給源として備え、
前記二次電池は、正極と、活物質を含む負極と、電解液とを備え、
前記活物質は、リチウムイオンを吸蔵放出可能であるコア部と、そのコア部の表面のうちの少なくとも一部に設けられた低結晶性または非結晶性の被覆部とを含み、
前記コア部はSiおよびOを構成元素として含み、そのSiに対するOの原子比x(O/Si)は0≦x<0.5を満たし、
前記被覆部はSiおよびOを構成元素として含み、そのSiに対するOの原子比y(O/Si)は0.5≦y≦1.8を満たし、
前記被覆部は空隙を有し、その空隙のうちの少なくとも一部に炭素含有材料が設けられている、
電子機器。
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US (1) | US20140349187A1 (ja) |
EP (1) | EP2797144B1 (ja) |
JP (1) | JP5982811B2 (ja) |
KR (1) | KR101950544B1 (ja) |
CN (1) | CN103988347B (ja) |
WO (1) | WO2013094404A1 (ja) |
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JP2013131325A (ja) | 2013-07-04 |
JP5982811B2 (ja) | 2016-08-31 |
US20140349187A1 (en) | 2014-11-27 |
EP2797144A1 (en) | 2014-10-29 |
KR101950544B1 (ko) | 2019-02-20 |
EP2797144A4 (en) | 2015-08-19 |
KR20140105460A (ko) | 2014-09-01 |
EP2797144B1 (en) | 2017-02-15 |
CN103988347A (zh) | 2014-08-13 |
CN103988347B (zh) | 2017-06-09 |
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